DS1922E [MAXIM]
High-Temperature Logger iButton with 8KB Data-Log Memory; 高温度记录器iButton ，带有8KB数据记录存储器
| 型号： | DS1922E |
| 厂家： | 
MAXIM INTEGRATED PRODUCTS |
| 描述： | High-Temperature Logger iButton with 8KB Data-Log Memory |
| 文件： | 总44页 (文件大小：387K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
19-4646; Rev 2; 6/09
High-Temperature Logger iButton with 8KB
Data-Log Memory
DS192E
♦ Communicates to Host with a Single Digital Signal
Up to 15.4kbps at Standard Speed or Up to
General Description
®
The DS1922E temperature logger iButton is a rugged,
125kbps in Overdrive Mode Using 1-Wire Protocol
self-sufficient system that measures temperature and
records the result in a protected memory section. The
recording is done at a user-defined rate. A total of 8192
8-bit readings or 4096 16-bit readings, taken at equidis-
tant intervals ranging from 1s to 273hr, can be stored.
Additionally, 576 bytes of SRAM store application-spe-
cific information. A mission to collect data can be pro-
grammed to begin immediately, after a user-defined
delay, or after a temperature alarm. Access to the
memory and control functions can be password pro-
tected. The DS1922E is configured and communicates
♦ Operating Temperature Range: ꢀ15°C to ꢀ140°C
Common iButton Features
♦ Digital Identification and Information by
Momentary Contact
♦ Unique Factory-Lasered 64-Bit Registration Number
Ensures Error-Free Device Selection and Absolute
Traceability Because No Two Parts Are Alike
♦ Built-In Multidrop Controller for 1-Wire Net
♦ Chip-Based Data Carrier Compactly Stores
®
with a host-computing device through the serial 1-Wire
Information
protocol, which requires only a single data lead and a
ground return. Every DS1922E is factory lasered with a
guaranteed unique 64-bit registration number that
allows for absolute traceability. The durable stainless-
steel package is highly resistant to environmental haz-
ards such as dirt, moisture, and shock.
♦ Data Can Be Accessed While Affixed to Object
♦ Button Shape is Self-Aligning with Cup-Shaped
Probes
♦ Durable Stainless-Steel Case Engraved with
Registration Number Withstands Harsh
Environments
Applications
High-Temperature Logging (Process Monitoring,
Industrial Temperature Monitoring)
♦ Easily Affixed with Self-Stick Adhesive Backing,
Latched by Its Flange, or Locked with a Ring
Pressed Onto Its Rim
Steam Sterilization
♦ Presence Detector Acknowledges When Reader
First Applies Voltage
Features
♦ Automatically Wakes Up, Measures Temperature,
and Stores Values in 8KB of Data-Log Memory in
8- or 16-Bit Format
♦ Meets UL 913 (4th Edit.); Intrinsically Safe
Apparatus: Approved Under Entity Concept for
Use in Class I, Division 1, Group A, B, C, and D
Locations*
♦ Digital Thermometer Measures Temperature with
8-Bit (0.5°C) or 11-Bit (0.0625°C) Resolution
Ordering Information
♦ Temperature Accuracy: ±1.5°C from ꢀ110°C to
ꢀ140°C, ±±°C typical from ꢀ15°C to ꢀ110°C
PART
TEMP RANGE
PIN-PACKAGE
♦ Water Resistant or Waterproof if Placed Inside
DS910± iButton Capsule (Exceeds Water
Resistant 3 ATM Requirements)
DS1922E-F5#
+15°C to +140°C
F5 iButton
# Denotes a RoHS-compliant device that may include lead(Pb)
that is exempt under the RoHS requirements.
♦ Sampling Rate from 1s Up to 2±3hr
♦ Programmable High and Low Trip Points for
Examples of Accessories
Temperature Alarms
PART
ACCESSORY
Mounting Lock Ring
iButton Capsule
♦ Programmable Recording Start Delay After Elapsed
DS9093RA
DS9107
Time or Upon a Temperature Alarm Trip Point
♦ Quick Access to Alarmed Devices Through 1-Wire
DS9490B
USB to 1-Wire Adapter
Conditional Search Function
♦ 5±6 Bytes of General-Purpose Memory
♦ Two-Level Password Protection of All Memory
Pin Configuration appears at end of data sheet.
and Configuration Registers
iButton and 1-Wire are registered trademarks of Maxim
Integrated Products, Inc.
*Application pending.
________________________________________________________________ Maxim Integrated Products
1
For pricing, delivery, and ordering information, please contact Maxim Direct at 1-888-629-4642,
or visit Maxim’s website at www.maxim-ic.com.
High-Temperature Logger iButton with 8KB
Data-Log Memory
ABSOLUTE MAXIMUM RATINGS
I/O Voltage Range to GND.......................................-0.3V to +6V
I/O Sink Current...................................................................20mA
Operating Temperature Range ........................+15°C to +140°C
Junction Temperature......................................................+150°C
Storage Temperature Range............................-25°C to +140°C*
*Storage or operation above +50°C significantly reduces battery life with an upper limit of 300hr cumulative at +140°C. The recom-
mended storage temperature for maximum battery lifetime is between +5°C and +35°C.
Stresses beyond those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. These are stress ratings only, and functional
operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to
absolute maximum rating conditions for extended periods may affect device reliability.
DS192E
ELECTRICAL CHARACTERISTICS
(V
PUP
= 3.0V to 5.25V.)
PARAMETER
SYMBOL
CONDITIONS
DS1922E (Note 1)
MIN
TYP
MAX
UNITS
Operating Temperature
I/O PIN GENERAL DATA
1-Wire Pullup Resistance
Input Capacitance
T
A
+15
+140
°C
R
(Notes 2, 3)
(Note 4)
2.2
800
10
kꢀ
pF
μA
V
PUP
C
100
6
IO
Input Load Current
I
L
I/O pin at V
PUP
High-to-Low Switching Threshold
Input Low Voltage
V
TL
(Notes 5, 6)
0.4
3.2
0.3
3.4
N/A
0.4
V
(Notes 2, 7)
V
IL
Low-to-High Switching Threshold
Switching Hysteresis
V
(Notes 5, 8)
0.7
V
TH
HY
OL
V
V
(Note 9)
0.09
V
Output Low Voltage
At 4mA (Note 10)
Standard speed, R
V
= 2.2kꢀ
= 2.2kꢀ
5
2
PUP
Overdrive speed, R
Recovery Time
(Note 2)
PUP
t
t
μs
REC
REH
Overdrive speed, directly prior to reset
pulse; R = 2.2kꢀ
5
PUP
Rising-Edge Hold-Off Time
Time Slot Duration (Note 2)
(Note 11)
0.6
65
8
2.0
μs
μs
Standard speed
t
Overdrive speed, V
> 4.5V
SLOT
PUP
Overdrive speed (Note 12)
I/O PIN 1-Wire RESET, PRESENCE-DETECT CYCLE
Standard speed, V
9.5
> 4.5V
480
690
48
70
15
15
2
720
720
80
PUP
Standard speed (Note 12)
Overdrive speed, V > 4.5V
Reset Low Time (Note 2)
t
μs
μs
RSTL
PUP
Overdrive speed (Note 12)
Standard speed, V > 4.5V
80
60
PUP
Presence-Detect High Time
t
PDH
Standard speed (Note 12)
Overdrive speed (Note 12)
63.5
7
2
_______________________________________________________________________________________
High-Temperature Logger iButton with 8KB
Data-Log Memory
DS192E
ELECTRICAL CHARACTERISTICS (continued)
(V
PUP
= 3.0V to 5.25V.)
PARAMETER
SYMBOL
CONDITIONS
MIN
1.5
1.5
0.15
60
TYP
MAX
5
UNITS
Standard speed, V
Standard speed
Overdrive speed
Standard speed, V
> 4.5V
PUP
PUP
Presence-Detect Fall Time
(Note 13)
t
μs
8
FPD
1
> 4.5V
240
287
24
28
75
75
9
Standard speed (Note 12)
Overdrive speed, V > 4.5V (Note 12)
60
Presence-Detect Low Time
t
μs
μs
PDL
7
PUP
Overdrive speed (Note 12)
7
Standard speed, V
Standard speed
Overdrive speed
> 4.5V
65
PUP
Presence-Detect Sample Time
(Note 2)
t
71.5
8
MSP
I/O PIN 1-Wire WRITE
Standard speed
60
6
120
12
Write-Zero Low Time
(Notes 2, 14)
t
μs
μs
Overdrive speed, V
> 4.5V (Note 12)
W0L
PUP
Overdrive speed (Note 12)
Standard speed
7.5
5
12
15
Write-One Low Time
(Notes 2, 14)
t
W1L
Overdrive speed
1
1.95
I/O PIN 1-Wire READ
Standard speed
Overdrive speed
Standard speed
Overdrive speed
5
1
15 - ꢁ
1.95 - ꢁ
15
Read Low Time
(Notes 2, 15)
t
μs
μs
RL
t
t
+ ꢁ
Read Sample Time
(Notes 2, 15)
RL
RL
t
MSR
+ ꢁ
1.95
REAL-TIME CLOCK (RTC)
See the RTC Accuracy
Min/
Month
Accuracy
graph
Frequency Deviation
ꢂ
F
0°C to +125°C
-600
+60
ppm
TEMPERATURE CONVERTER
8-bit mode
30
75
Conversion Time
(Note 16)
t
ms
s
CONV
16-bit mode (11 bits)
240
600
Thermal Response Time
Constant (Note 17)
ꢃ
iButton package
130
7
RESP
+15°C to +110°C (Note 20)
+110°C to +140°C
Conversion Error (Notes 18, 19)
ꢂꢄ
°C
-1.5
+1.5
300
300
Cycle = ramp from +25°C to > +125°C
and back to +25°C (Note 21)
Temperature Cycles
Operating Lifetime
N
Cycles
Hours
TCY
t
Temperature > +125°C (Note 21)
LIFE
_______________________________________________________________________________________
3
High-Temperature Logger iButton with 8KB
Data-Log Memory
Note 1: Operation above +125°C is restricted to mission operations only. Communication and 1-Wire pin specifications are not
specified for operation above +125°C.
Note 2: System requirement.
Note 3: Maximum allowable pullup resistance is a function of the number of 1-Wire devices in the system and 1-Wire recovery
times. The specified value here applies to systems with only one device and with the minimum 1-Wire recovery times. For
more heavily loaded systems, an active pullup such as that in the DS2480B can be required.
Note 4: Capacitance on the data pin could be 800pF when V
is first applied. If a 2.2kΩ resistor is used to pull up the data line
PUP
2.5µs after V
has been applied, the parasite capacitance does not affect normal communications.
PUP
Note 5:
V
V
and V are a function of the internal supply voltage, which is a function of V
and the 1-Wire recovery times. The
TL
TH
TH
PUP
TL
DS192E
and V maximum specifications are valid at V
(5.25V). In any case, V < V < V
.
TL
PUPMAX
TH
PUP
Note 6: Voltage below which, during a falling edge on I/O, a logic 0 is detected.
Note ±: The voltage on I/O must be less than or equal to V whenever the master drives the line low.
ILMAX
Note 8: Voltage above which, during a rising edge on I/O, a logic 1 is detected.
Note 9: After V is crossed during a rising edge on I/O, the voltage on I/O must drop by V to be detected as logic 0.
TH
HY
Note 10: The I-V characteristic is linear for voltages less than 1V.
Note 11: The earliest recognition of a negative edge is possible at t
after V has been previously reached.
TH
REH
Note 12: Numbers in bold are not in compliance with the published iButton standards. See the Comparison Table.
Note 13: Interval during the negative edge on I/O at the beginning of a presence-detect pulse between the time at which the volt-
age is 90% of V
and the time at which the voltage is 10% of V
.
PUP
PUP
Note 14: ε in Figure 13 represents the time required for the pullup circuitry to pull the voltage on I/O up from V to V . The actual
IL
TH
maximum duration for the master to pull the line low is t
+ t - ε and t
+ t - ε, respectively.
W0LMAX F
W1LMAX
F
Note 15: δ in Figure 13 represents the time required for the pullup circuitry to pull the voltage on I/O up from V to the input high
IL
threshold of the bus master. The actual maximum duration for the master to pull the line low is t
Note 16: To conserve battery power, use 8-bit temperature logging whenever possible.
Note 1±: This number was derived from a test conducted by Cemagref in Antony, France, in July 2000:
www.cemagref.fr/English/index.htm Test Report No. E42.
+ t .
RLMAX
F
Note 18: Includes +0.1°C/-0.2°C calibration chamber measurement uncertainty.
Note 19: Warning: Not for use as the sole method of measuring or tracking temperature in products and articles that could affect
the health or safety of persons, plants, animals, or other living organisms, including but not limited to foods, beverages,
pharmaceuticals, medications, blood and blood products, organs, and flammable and combustible products. User shall
assure that redundant (or other primary) methods of testing and determining the handling methods, quality, and fitness of
the articles and products should be implemented. Temperature tracking with this product, where the health or safety of
the aforementioned persons or things could be adversely affected, is only recommended when supplemental or redun-
dant information sources are used. Data-logger products are 100% tested and calibrated at time of manufacture by
Maxim to ensure that they meet all data sheet parameters, including temperature accuracy. User shall be responsible for
proper use and storage of this product. As with any sensor-based product, user shall also be responsible for occasionally
rechecking the temperature accuracy of the product to ensure it is still operating properly.
Note 20: Guaranteed by design and not production tested.
Note 21: Devices leave the factory after having been run through a few cycles above +125°C. This is required for calibration of the
device but should not affect lifetime of the device as specified. However, this process results in a nonzero value in the
Device Samples Counter register (0223h–0225h), which provides evidence the device has been factory calibrated.
4
_______________________________________________________________________________________
High-Temperature Logger iButton with 8KB
Data-Log Memory
DS192E
COMPARISON TABLE
LEGACY VALUES
STANDARD SPEED OVERDRIVE SPEED
(μs) (μs)
DS1922E VALUES
STANDARD SPEED
(μs)
OVERDRIVE SPEED
(μs)
PARAMETER
MIN
61
MAX
MIN
7
MAX
MIN
65*
690
15
MAX
MIN
9.5
70
2
MAX
t
t
t
t
t
(including t
)
(undefined)
(undefined)
60
(undefined)
(undefined)
720
(undefined)
SLOT
REC
480
15
48
2
80
6
80
7
RSTL
PDH
PDL
63.5
60
240
8
24
16
60
287
7
28
12
60
120
6
60
120
7.5
W0L
*Intentional change; longer recovery time requirement due to modified 1-Wire front-end.
Note: Numbers in bold are not in compliance with the published iButton standards.
iButton CAN PHYSICAL SPECIFICATION
SIZE
See the Package Information section.
WEIGHT
Ca. 3.3 grams
Meets UL 913 (4th Edit.); Intrinsically Safe Apparatus, approval under Entity Concept for use in Class I,
Division 1, Group A, B, C, and D Locations*.
SAFETY
*Application pending.
RTC Accuracy
RTC ACCURACY (TYPICAL)
2
0
-2
-4
-6
-8
-10
-12
-14
-16
-18
15
25
35
45
55
65
75
85
95
105
115
125
135
TEMPERATURE (°C)
_______________________________________________________________________________________
5
High-Temperature Logger iButton with 8KB
Data-Log Memory
ROM command byte executed at standard speed, the
Detailed Description
device enters Overdrive Mode, where all subsequent
With its extended temperature range, the DS1922E is
communication occurs at a higher speed. The protocol
well suited to monitor processes that require tempera-
required for these ROM function commands is
tures well above the boiling point of water, such as pas-
described in Figure 11. After a ROM function command
teurization of food items. Note that the initial sealing
is successfully executed, the memory and control func-
level of the DS1922E achieves the equivalent of IP56.
tions become accessible and the master can provide
Aging and use conditions can degrade the integrity of
any one of the eight available commands. The protocol
the seal over time, so for applications with significant
for these memory and control function commands is
exposure to liquids, sprays, or other similar environ-
described in Figure 9. All data is read and written
ments, it is recommended to place the DS1922E in the
least significant bit first.
DS192E
DS9107 iButton capsule. The DS9107 provides a water-
tight enclosure that has been rated to IP68 (refer to
Application Note 4126: Understanding the IP (Ingress
Protection) Ratings of iButton Data Loggers and
Capsules). Software for setup and data retrieval through
the 1-Wire interface is available for free download from
the iButton website (www.ibutton.com). This software
also includes drivers for the serial and USB port of a PC
and routines to access the general-purpose memory for
storing application- or equipment-specific data files.
Parasite Power
The block diagram (Figure 1) shows the parasite-pow-
ered circuitry. This circuitry “steals” power whenever the
I/O input is high. I/O provides sufficient power as long as
the specified timing and voltage requirements are met.
The advantages of parasite power are two-fold: 1) By
parasiting off this input, battery power is not consumed
for 1-Wire ROM function commands, and 2) if the battery
is exhausted for any reason, the ROM can still be read
normally. The remaining circuitry of the DS1922E is sole-
ly operated by battery energy.
Overview
The block diagram in Figure 1 shows the relationships
between the major control and memory sections of the
DS1922E. The device has five main data components:
64-bit lasered ROM; 256-bit scratchpad; 576-byte gen-
eral-purpose SRAM; two 256-bit register pages of time-
keeping, control, status, and counter registers, and
passwords; and 8192 bytes of data-logging memory.
Except for the ROM and the scratchpad, all other mem-
ory is arranged in a single linear address space. The
data-logging memory, counter registers, and several
other registers are read only for the user. Both register
pages are write protected while the device is pro-
grammed for a mission. The password registers, one for
a read password and another one for a read/write pass-
word, can only be written, never read.
64-Bit Lasered ROM
Each DS1922E contains a unique ROM code that is 64
bits long. The first 8 bits are a 1-Wire family code. The
next 48 bits are a unique serial number. The last 8 bits
are a cyclic redundancy check (CRC) of the first 56 bits
(see Figure 3 for details). The 1-Wire CRC is generated
using a polynomial generator consisting of a shift regis-
ter and XOR gates as shown in Figure 4. The polynomi-
al is X8 + X5 + X4 + 1. Additional information about the
1-Wire CRC is available in Application Note 27:
Understanding and Using Cyclic Redundancy Checks
with Maxim iButton Products.
The shift register bits are initialized to 0. Then, starting
with the least significant bit of the family code, one bit
at a time is shifted in. After the 8th bit of the family code
has been entered, the serial number is entered. After
the last bit of the serial number has been entered, the
shift register contains the CRC value. Shifting in the 8
bits of CRC returns the shift register to all 0s.
Figure 2 shows the hierarchical structure of the 1-Wire
protocol. The bus master must first provide one of the
eight ROM function commands: Read ROM, Match
ROM, Search ROM, Conditional Search ROM, Skip
ROM, Overdrive-Skip ROM, Overdrive-Match ROM, or
Resume Command. Upon completion of an Overdrive
6
_______________________________________________________________________________________
High-Temperature Logger iButton with 8KB
Data-Log Memory
DS192E
ROM
FUNCTION
CONTROL
64-BIT
LASERED
ROM
PARASITE-POWERED
CIRCUITRY
1-Wire PORT I/O
256-BIT
SCRATCHPAD
MEMORY
FUNCTION
CONTROL
3V LITHIUM
DS1922E
GENERAL-PURPOSE
SRAM
(512 BYTES)
INTERNAL
32.768kHz
TIMEKEEPING,
CONTROL REGISTERS,
AND COUNTERS
REGISTER PAGES
(64 BYTES)
OSCILLATOR
USER MEMORY
(64 BYTES)
THERMAL
SENSE
ADC
CONTROL
LOGIC
DATA-LOG MEMORY
8KB
Figure 1. Block Diagram
_______________________________________________________________________________________
±
High-Temperature Logger iButton with 8KB
Data-Log Memory
1-Wire NET
BUS
MASTER
OTHER DEVICES
DS1922E
DS192E
COMMAND LEVEL:
AVAILABLE COMMANDS:
DATA FIELD AFFECTED:
READ ROM
64-BIT ROM, RC-FLAG
MATCH ROM
64-BIT ROM, RC-FLAG
SEARCH ROM
64-BIT ROM, RC-FLAG
1-Wire ROM
FUNCTION COMMANDS
CONDITIONAL SEARCH ROM
SKIP ROM
64-BIT ROM, RC-FLAG, ALARM FLAGS, SEARCH CONDITIONS
RC-FLAG
RESUME
RC-FLAG
OVERDRIVE-SKIP ROM
OVERDRIVE-MATCH ROM
RC-FLAG, OD-FLAG
64-BIT ROM, RC-FLAG, OD-FLAG
WRITE SCRATCHPAD
256-BIT SCRATCHPAD, FLAGS
READ SCRATCHPAD
256-BIT SCRATCHPAD
COPY SCRATCHPAD WITH PW
READ MEMORY WITH PW AND CRC
CLEAR MEMORY WITH PW
512-BYTE DATA MEMORY, REGISTERS, FLAGS, PASSWORDS
MEMORY, REGISTERS, PASSWORDS
MISSION TIMESTAMP, MISSION SAMPLES COUNTER,
START DELAY, ALARM FLAGS, PASSWORDS
MEMORY ADDRESSES 020Ch TO 020Dh
FLAGS, TIMESTAMP, MEMORY ADDRESSES
020Ch TO 020Dh (WHEN LOGGING)
FLAGS
DS1922E-SPECIFIC
MEMORY FUNCTION COMMANDS
FORCED CONVERSION
START MISSION WITH PW
STOP MISSION WITH PW
Figure 2. Hierarchical Structure for 1-Wire Protocol
MSB
LSB
LSB
8-BIT
CRC CODE
8-BIT FAMILY CODE
(41h)
48-BIT SERIAL NUMBER
MSB
LSB MSB
LSB MSB
Figure 3. 64-Bit Lasered ROM
8
5
4
POLYNOMIAL = X + X + X + 1
1ST
2ND
3RD
4TH
5TH
6TH
7TH
8TH
STAGE
STAGE
STAGE
STAGE
STAGE
STAGE
STAGE
STAGE
0
1
2
3
4
5
6
7
8
X
X
X
X
X
X
X
X
X
INPUT DATA
Figure 4. 1-Wire CRC Generator
_______________________________________________________________________________________
8
High-Temperature Logger iButton with 8KB
Data-Log Memory
DS192E
memory can be written at any time. The access type for
the register pages is register-specific and depends on
whether the device is programmed for a mission.
Figure 6 shows the details. The data-log memory is
read only for the user. It is written solely under supervi-
sion of the on-chip control logic. Due to the special
behavior of the write access logic (write scratchpad,
copy scratchpad), it is recommended to only write full
pages at a time. This also applies to the register pages.
See the Address Registers and Transfer Status section
for details.
Memory
Figure 5 shows the DS1922E memory map. Pages 0 to
15 contain 512 bytes of general-purpose SRAM. The
various registers to set up and control the device fill
pages 16 and 17, called register pages 1 and 2 (see
Figure 6 for details). Pages 18 and 19 can be used as
extension of the general-purpose memory. The data-log
logging memory starts at address 1000h (page 128)
and extends over 256 pages. The memory pages 20 to
127 are reserved for future extensions. The scratchpad
is an additional page that acts as a buffer when writing
to the SRAM memory or the register page. The data
32-BYTE INTERMEDIATE STORAGE
SCRATCHPAD
ADDRESS
32-BYTE GENERAL-PURPOSE SRAM
(R/W)
0000h TO 001Fh
PAGE 0
PAGES 1 TO 15
PAGE 16
0020h TO 01FFh
0200h TO 021Fh
0220h TO 023Fh
0240h TO 025Fh
0260h TO 027Fh
0280h TO 0FFFh
1000h TO 2FFFh
GENERAL-PURPOSE SRAM (R/W)
32-BYTE REGISTER PAGE 1
32-BYTE REGISTER PAGE 2
PAGE 17
GENERAL-PURPOSE SRAM (R/W)
GENERAL-PURPOSE SRAM (R/W)
(RESERVED FOR FUTURE EXTENSIONS)
DATA-LOG MEMORY (READ ONLY)
PAGE 18
PAGE 19
PAGES 20 TO 127
PAGES 128 TO 383
Figure 5. Memory Map
_______________________________________________________________________________________
9
High-Temperature Logger iButton with 8KB
Data-Log Memory
ADDRESS
0200h
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT 2
BIT 1
BIT 0
FUNCTION
ACCESS*
0
0
10 Seconds
10 Minutes
Single Seconds
Single Minutes
0201h
20 Hour
AM/PM
Real-
Time Clock
Registers
0202h
0203h
0204h
0
0
12/24
10 Hour
Single Hours
Single Date
R/W
R
0
0
10 Date
DS192E
10
Months
CENT
0
Single Months
Single Years
0205h
0206h
0207h
0208h
0209h
020Ah
020Bh
020Ch
020Dh
020Eh
020Fh
10 Years
Low Byte
Sample
Rate
R/W
R/W
R/W
R
R
R
R
R
R
0
0
Low Byte
0
High Byte
Low Threshold
High Threshold
Temperature
Alarms
(No Function with the DS1922E)
(No Function with the DS1922E)
—
0
0
0
0
0
Latest
Temperature
High Byte
(No Function with the DS1922E)
(No Function with the DS1922E)
—
R
Temperature
Alarm
0210h
0
0
0
0
0
ETHA
ETLA
R/W
R/W
R
Enable
0211h
0212h
1
0
1
0
1
0
1
0
1
0
1
0
0
0
—
R
R
EHSS
EOSC
RTC Control R/W
Mission
R/W
0213h
0214h
0215h
1
BOR
1
1
1
1
SUTA
RO
1
(X)
0
TLFS
0
ETL
TLF
0
R
R
R
Control
1
0
0
0
THF
MIP
Alarm Status
R
R
General
Status
WFTA MEMCLR
0216h
0217h
0218h
Low Byte
Center Byte
High Byte
Start
Delay
Counter
R/W
R
*The left entry in the ACCESS column is valid between missions. The right entry shows the applicable access type while a
mission is in progress.
Figure 6. DS1922E Register Pages Map
10 ______________________________________________________________________________________
High-Temperature Logger iButton with 8KB
Data-Log Memory
DS192E
ADDRESS
0219h
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT 2
BIT 1
BIT 0
FUNCTION
ACCESS*
0
0
10 Seconds
10 Minutes
Single Seconds
Single Minutes
021Ah
20 Hour
AM/PM
021Bh
021Ch
021Dh
0
0
12/24
10 Hour
Single Hours
Single Date
Mission
Timestamp
R
R
0
0
10 Date
10
Months
CENT
0
Single Months
Single Years
021Eh
021Fh
0220h
0221h
0222h
0223h
0224h
0225h
0226h
0227h
0228h
…
10 Years
(No Function; Reads 00h)
Low Byte
—
R
R
R
R
Mission
Samples
Counter
Center Byte
High Byte
Low Byte
Device
Samples
Counter
R
R
Center Byte
High Byte
Configuration Code
EPW
Flavor
R
R
R
PW Control
R/W
First Byte
…
Read
Access
Password
W
W
R
—
—
R
022Fh
0230h
…
Eighth Byte
First Byte
…
Full
Access
Password
0237h
0238h
…
Eighth Byte
(No Function; All These Bytes Read 00h)
—
023Fh
*The left entry in the ACCESS column is valid between missions. The right entry shows the applicable access type while a
mission is in progress.
Figure 6. DS1922E Register Pages Map (continued)
______________________________________________________________________________________ 11
High-Temperature Logger iButton with 8KB
Data-Log Memory
Sample Rate
Detailed Register Descriptions
The content of the Sample Rate register (addresses
0206h, 0207h) specifies the time elapse (in seconds if
EHSS = 1, or minutes if EHSS = 0) between two tem-
perature-logging events. The sample rate can be any
value from 1 to 16,383, coded as an unsigned 14-bit
binary number. If EHSS = 1, the shortest time between
logging events is 1s and the longest (sample rate =
3FFFh) is 4.55hr. If EHSS = 0, the shortest is 1min and
the longest time is 273.05hr (sample rate = 3FFFh). The
EHSS bit is located in the RTC Control register at
address 0212h. It is important that the user sets the
EHSS bit accordingly while setting the Sample Rate
register. Writing a sample rate of 0000h results in a
sample rate = 0001h, causing the DS1922E to log
the temperature either every minute or every sec-
ond depending upon the state of the EHSS bit.
Timekeeping and Calendar
The RTC and calendar information is accessed by
reading/writing the appropriate bytes in the register
page, address 0200h to 0205h. For readings to be
valid, all RTC registers must be read sequentially start-
ing at address 0200h. Some of the RTC bits are set to
0. These bits always read 0 regardless of how they are
written. The number representation of the RTC registers
is binary-coded decimal (BCD) format.
DS192E
The DS1922E’s RTC can run in either 12hr or 24hr
mode. Bit 6 of the Hours register (address 0202h) is
defined as the 12hr or 24hr mode select bit. When high,
the 12hr mode is selected. In the 12hr mode, bit 5 is
the AM/PM bit with logic 1 being PM. In the 24hr mode,
bit 5 is the 20hr bit (20hr to 23hr). The CENT bit, bit 7 of
the Months register, can be written by the user. This bit
changes its state when the years counter transitions
from 99 to 00.
The calendar logic is designed to automatically com-
pensate for leap years. For every year value that is
either 00 or a multiple of 4, the device adds a 29th of
February. This works correctly up to (but not including)
the year 2100.
RTC Registers
ADDRESS
0200h
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT 2
BIT 1
BIT 0
0
0
10 Seconds
10 Minutes
Single Seconds
0201h
Single Minutes
Single Hours
20 Hour
AM/PM
0202h
0
12/24
10 Hour
0203h
0204h
0205h
0
0
0
10 Date
Single Date
Single Months
Single Years
CENT
0
10 Months
10 Years
Note: During a mission, there is only read access to these registers. Bit cells marked “0” always read 0 and cannot be written to 1.
Sample Rate Register
ADDRESS
0206h
BIT 7
BIT 6
BIT 5
BIT 4
Sample Rate Low
Sample Rate High
BIT 3
BIT 2
BIT 1
BIT 0
0207h
0
0
Note: During a mission, there is only read access to these registers. Bit cells marked “0” always read 0 and cannot be written to 1.
12 ______________________________________________________________________________________
High-Temperature Logger iButton with 8KB
Data-Log Memory
DS192E
This equation is valid for converting temperature read-
ings stored in the data-log memory as well as for data
read from the Latest Temperature Conversion Result
register.
Temperature Conversion
The DS1922E’s temperature range begins at +15°C
and ends at +140°C. Temperature values are repre-
sented as an 8- or 16-bit unsigned binary number with
a resolution of 0.5°C in 8-bit mode and 0.0625°C in
16-bit mode.
To specify the temperature alarm thresholds, the previ-
ous equations are resolved to:
The higher temperature byte TRH is always valid. In
16-bit mode, only the three highest bits of the lower
byte TRL are valid. The five lower bits all read 0. TRL is
undefined if the device is in 8-bit temperature mode. An
out-of-range temperature reading is indicated as 00h or
0000h when too cold and FFh or FFE0h when too hot.
TALM = 2 x ϑ(°C) - 28
Because the temperature alarm threshold is only one
byte, the resolution or temperature increment is limited
to 0.5°C. The TALM value must be converted into hexa-
decimal format before it can be written to one of the
Temperature Alarm Threshold registers (Low Alarm
address 0208h; High Alarm address 0209h).
Independent of the conversion mode (8- or 16-bit), only
the most significant byte of a temperature conversion is
used to determine whether an alarm is generated.
With TRH and TRL representing the decimal equivalent
of a temperature reading, the temperature value is cal-
culated as:
ϑ(°C) = TRH/2 + 14 + TRL/512 (16-bit mode,
TLFS = 1, see address 0213h)
ϑ(°C) = TRH/2 + 14 (8-bit mode, TLFS = 0,
see address 0213h)
Latest Temperature Conversion Result Register
ADDRESS
020Ch
BIT 7
T2
BIT 6
T1
BIT 5
T0
BIT 4
0
BIT 3
0
BIT 2
0
BIT 1
0
BIT 0
0
BYTE
TRL
020Dh
T10
T9
T8
T7
T6
T5
T4
T3
TRH
Table 1. Temperature Conversion Examples
TRH
TRL
MODE
ꢀ(°C)
HEX
54h
17h
54h
17h
DECIMAL
HEX
DECIMAL
8-Bit
8-Bit
84
23
84
23
—
—
—
—
0
56.0
25.5
16-Bit
16-Bit
00h
60h
56.0000
25.6875
96
Table 2. Temperature Alarm Threshold Examples
TALM
ꢀ(°C)
HEX
67h
20h
DECIMAL
103
65.5
30.0
32
______________________________________________________________________________________ 13
High-Temperature Logger iButton with 8KB
Data-Log Memory
Temperature Sensor Control Register
ADDRESS
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT 2
BIT 1
BIT 0
0210h
0
0
0
0
0
0
ETHA
ETLA
Note: During a mission, there is only read access to this register. Bits 2 to 7 have no function. They always read 0 and cannot be
written to 1.
RTC Control Register
DS192E
ADDRESS
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT 2
BIT 1
BIT 0
0212h
0
0
0
0
0
0
EHSS
EOSC
Note: During a mission, there is only read access to this register. Bits 2 to 7 have no function. They always read 0 and cannot be
written to 1.
Temperature Sensor Alarm
The DS1922E has two Temperature Alarm Threshold
registers (address 0208h, 0209h) to store values that
determine whether a critical temperature has been
reached. A temperature alarm is generated if the
device measures an alarming temperature and the
alarm signaling is enabled. The bits ETLA and ETHA
that enable the temperature alarm are located in the
Temperature Sensor Control register. The temperature
alarm flags TLF and THF are found in the Alarm Status
register at address 0214h.
RTC Control
To minimize the power consumption of a DS1922E, the
RTC oscillator should be turned off when the device is
not in use. The oscillator on/off bit is located in the RTC
Control register. This register also includes the EHSS
bit, which determines whether the sample rate is speci-
fied in seconds or minutes.
Bit 1: Enable High-Speed Sample (EHSS). This bit
controls the speed of the sample rate counter. When set
to logic 0, the sample rate is specified in minutes. When
set to logic 1, the sample rate is specified in seconds.
Bit 1: Enable Temperature High Alarm (ETHA). This
bit controls whether, during a mission, the temperature
high alarm flag (THF) may be set, if a temperature con-
version results in a value equal to or higher than the
value in the Temperature High Alarm Threshold register.
If ETHA is 1, temperature high alarms are enabled. If
ETHA is 0, temperature high alarms are not generated.
Bit 0: Enable Oscillator (EOSC). This bit controls the
crystal oscillator of the RTC. When set to logic 1, the
oscillator starts. When written to logic 0, the oscillator
stops and the device is in a low-power data-retention
mode. This bit must be 1 for normal operation. A Forced
Conversion or Start Mission command automatically
starts the RTC by changing the EOSC bit to logic 1.
Bit 0: Enable Temperature Low Alarm (ETLA). This
bit controls whether, during a mission, the temperature
low alarm flag (TLF) may be set, if a temperature con-
version results in a value equal to or lower than the
value in the Temperature Low Alarm Threshold register.
If ETLA is 1, temperature low alarms are enabled. If
ETLA is 0, temperature low alarms are not generated.
14 ______________________________________________________________________________________
High-Temperature Logger iButton with 8KB
Data-Log Memory
DS192E
Mission Control Register
ADDRESS
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT 2
BIT 1
BIT 0
0213h
1
1
SUTA
RO
(X)
TLFS
0
ETL
Note: During a mission, there is only read access to this register. Bits 6 and 7 have no function. They always read 1 and cannot be
written to 0. Bits 1 and 3 control functions that are not available with the DS1922E. Bit 1 must be set to 0. Under this condition the
setting of bit 3 becomes a “don’t care.”
Bit 4: Rollover Control (RO). This bit controls whether,
during a mission, the data-log memory is overwritten
with new data or whether data logging is stopped once
the data-log memory is full. Setting this bit to 1 enables
the rollover and data logging continues at the begin-
ning, overwriting previously collected data. If this bit is
0, the logging and conversions stop once the data-log
memory is full. However, the RTC continues to run and
the MIP bit remains set until the Stop Mission command
is performed.
Mission Control
The DS1922E is set up for its operation by writing
appropriate data to its special function registers, which
are located in the two register pages. The settings in
the Mission Control register determine which format (8
or 16 bits) applies and whether old data can be over-
written by new data once the data-log memory is full.
An additional control bit can be set to tell the DS1922E
to wait with logging data until a temperature alarm is
encountered.
Bit 2: Temperature Logging Format Selection
(TLFS). This bit specifies the format used to store tem-
perature readings in the data-log memory. If this bit is
0, the data is stored in 8-bit format. If this bit is 1, the
16-bit format is used (higher resolution). With 16-bit for-
mat, the most significant byte is stored at the lower
address.
Bit 5: Start Mission Upon Temperature Alarm
(SUTA). This bit specifies whether a mission begins
immediately (includes delayed start) or if a temperature
alarm is required to start the mission. If this bit is 1, the
device performs an 8-bit temperature conversion at the
selected sample rate and begins with data logging only
if an alarming temperature (high alarm or low alarm)
was found. The first logged temperature is when the
alarm occurred. However, the mission sample counter
does not increment. This functionality is guaranteed by
design and not production tested.
Bit 0: Enable Temperature Logging (ETL). To set up
the device for a temperature-logging mission, this bit
must be set to logic 1. The recorded temperature val-
ues start at address 1000h.
______________________________________________________________________________________ 15
High-Temperature Logger iButton with 8KB
Data-Log Memory
Alarm Status Register
ADDRESS
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT 2
BIT 1
BIT 0
0214h
BOR
1
1
1
0
0
THF
TLF
Note: There is only read access to this register. Bits 4 to 6 have no function. They always read 1. Bits 2 and 3 have no function with
the DS1922E. They always read 0. The alarm status bits are cleared simultaneously when the Clear Memory Function is invoked. See
memory and control functions for details.
General Status Register
DS192E
ADDRESS
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT 2
BIT 1
BIT 0
0215h
1
1
0
WFTA
MEMCLR
0
MIP
0
Note: There is only read access to this register. Bits 0, 2, 5, 6, and 7 have no function.
Alarm Status
General Status
The fastest way to determine whether a programmed
temperature threshold was exceeded during a mission
is through reading the Alarm Status register. In a net-
worked environment that contains multiple DS1922E
iButtons, the devices that encountered an alarm can
quickly be identified by means of the Conditional
Search command (see the 1-Wire ROM Function
Commands section). The temperature alarm only
occurs if enabled (see the Temperature Sensor Alarm
section). The BOR alarm is always enabled.
The information in the General Status register tells the
host computer whether a mission-related command
was executed successfully. Individual status bits indi-
cate whether the DS1922E is performing a mission,
waiting for a temperature alarm to trigger the logging of
data or whether the data from the latest mission has
been cleared.
Bit 4: Waiting for Temperature Alarm (WFTA). If this
bit reads 1, the Mission Start Upon Temperature Alarm
was selected and the Start Mission command was suc-
cessfully executed, but the device has not yet experi-
enced the temperature alarm. This bit is cleared after a
temperature alarm event, but is not affected by the
Clear Memory command. Once set, WFTA remains set
if a mission is stopped before a temperature alarm
occurs. To clear WFTA manually before starting a new
mission, set the high temperature alarm (address
0209h) to +15°C and perform a forced conversion.
Bit ±: Battery-On Reset Alarm (BOR). If this bit reads
1, the device has performed a power-on reset. This
indicates that the device has experienced a shock big
enough to interrupt the internal battery power supply.
The device may still appear functional, but it has lost its
factory calibration. Any data found in the data-log
memory should be disregarded.
Bit 1: Temperature High Alarm Flag (THF). If this bit
reads 1, there was at least one temperature conversion
during a mission revealing a temperature equal to or
higher than the value in the Temperature High Alarm
register. A forced conversion can affect the THF bit.
This bit can also be set with the initial alarm in the
SUTA = 1 mode.
Bit 3: Memory Cleared (MEMCLR). If this bit reads 1,
the Mission Timestamp, mission samples counter, and
all the alarm flags of the Alarm Status register have
been cleared in preparation of a new mission.
Executing the Clear Memory command clears these
memory sections. The MEMCLR bit returns to 0 as soon
as a new mission is started by using the Start Mission
command. The memory must be cleared for a mission
to start.
Bit 0: Temperature Low Alarm Flag (TLF). If this bit
reads 1, there was at least one temperature conversion
during a mission revealing a temperature equal to or
lower than the value in the Temperature Low Alarm reg-
ister. A forced conversion can affect the TLF bit. This
bit can also be set with the initial alarm in the SUTA = 1
mode.
Bit 1: Mission in Progress (MIP). If this bit reads 1,
the device has been set up for a mission and this mis-
sion is still in progress. The MIP bit returns from logic 1
to logic 0 when a mission is ended. See the Start
Mission and Stop Mission function commands.
16 ______________________________________________________________________________________
High-Temperature Logger iButton with 8KB
Data-Log Memory
DS192E
Mission Start Delay Counter Register
ADDRESS
0216h
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT 2
BIT 1
BIT 0
Delay Low Byte
0217h
Delay Center Byte
Delay High Byte
0218h
Note: During a mission, there is only read access to this register.
Mission Timestamp Register
ADDRESS
0219h
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT 2
BIT 1
BIT 0
0
0
10 Seconds
10 Minutes
Single Seconds
021Ah
Single Minutes
Single Hours
20 Hours
AM/PM
021Bh
0
12/24
10 Hours
021Ch
021Dh
021Eh
0
0
0
10 Date
Single Date
Single Months
Single Years
CENT
0
10 Months
10 Years
Note: There is only read access to this register.
Mission Samples Counter Register
ADDRESS
0220h
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT 2
BIT 1
BIT 0
Low Byte
0221h
Center Byte
High Byte
0222h
Note: There is only read access to this register.
Mission Start Delay
The content of the Mission Start Delay Counter register
tells how many minutes must expire from the time a
mission was started until the first measurement of the
mission takes place (SUTA = 0) or until the device
starts testing the temperature for a temperature alarm
(SUTA = 1). The Mission Start Delay is stored as an
unsigned 24-bit integer number. The maximum delay is
16,777,215min, equivalent to 11,650 days or roughly
31yr. If the start delay is nonzero and the SUTA bit is
set to 1, first the delay must expire before the device
starts testing for temperature alarms to begin logging
data.
Mission Timestamp
The Mission Timestamp register indicates the date and
time of the first temperature sample of the mission.
There is only read access to the Mission Timestamp
register.
Mission Progress Indicator
Depending on settings in the Mission Control register
(address 0213h), the DS1922E logs temperature in 8-bit
or 16-bit format. The Mission Samples Counter together
with the starting address and the logging format (8 or 16
bits) provide the information to identify valid blocks of
data that have been gathered during the current
(MIP = 1) or latest mission (MIP = 0). See the Data-Log
Memory Usage section for an illustration.
For a typical mission, the Mission Start Delay is 0. If a
mission is too long for a single DS1922E to store all
readings at the selected sample rate, one can use sev-
eral devices and set the Mission Start Delay for the sec-
ond device to start recording as soon as the memory of
the first device is full, and so on. The RO bit in the
Mission Control register (address 0213h) must be set to
0 to prevent overwriting of collected data once the
data-log memory is full.
The number read from the mission samples counter
indicates how often the DS1922E woke up during a
mission to measure temperature. The number format is
24-bit unsigned integer. The mission samples counter
is reset through the Clear Memory command.
______________________________________________________________________________________ 1±
High-Temperature Logger iButton with 8KB
Data-Log Memory
Device Samples Counter Register
ADDRESS
0223h
BIT 7
BIT 6
BIT 5
BIT 4
Low Byte
BIT 3
BIT 2
BIT 1
BIT 0
0224h
Center Byte
High Byte
0225h
Note: There is only read access to this register.
DS192E
Device Configuration Register
ADDRESS
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT 2
BIT 1
BIT 0
PART
0
0
0
0
1
0
0
1
1
0
0
1
0
1
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
DS2422
DS1923
DS1922L
DS1922T
DS1922E
0226h
Note: There is only read access to this register.
Password Control Register
ADDRESS
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT 2
BIT 1
BIT 0
0227h
EPW
Note: During a mission, there is only read access to this register.
Other Indicators
The Device Samples Counter register is similar to the
Mission Samples Counter register. During a mission this
counter increments whenever the DS1922E wakes up
to measure and log data and when the device is testing
for a temperature alarm in SUTA mode. Between mis-
sions the counter increments whenever the Forced
Conversion command is executed. This way the Device
Samples Counter register functions like a gas gauge for
the battery that powers the iButton.
Security by Password
The DS1922E is designed to use two passwords that
control read access and full access. Reading from or
writing to the scratchpad as well as the forced conver-
sion command does not require a password. The pass-
word must be transmitted immediately after the
command code of the memory or control function. If
password checking is enabled, the password transmit-
ted is compared to the passwords stored in the device.
The data pattern stored in the Password Control regis-
ter determines whether password checking is enabled.
The Device Samples Counter register is reset to zero
when the iButton is assembled. The counter increments
a couple of times during final test. The number format is
24-bit unsigned integer. The maximum number that can
be represented in this format is 16,777,215.
To enable password checking, the EPW bits need to
form a binary pattern of 10101010 (AAh). The default
pattern of EPW is different from AAh. If the EPW pattern
is different from AAh, any pattern is accepted as long
as it has a length of exactly 64 bits. Once enabled,
changing the passwords and disabling password
checking requires the knowledge of the current full-
access password.
The code in the Device Configuration register allows
the master to distinguish between the DS2422 chip and
different versions of the DS1922 iButtons. The Device
Configuration Register table shows the codes assigned
to the various devices.
18 ______________________________________________________________________________________
High-Temperature Logger iButton with 8KB
Data-Log Memory
DS192E
Read Access Password Register
ADDRESS
0228h
0229h
…
BIT 7
RP7
BIT 6
RP6
BIT 5
RP5
BIT 4
RP4
BIT 3
RP3
BIT 2
RP2
BIT 1
RP1
BIT 0
RP0
RP15
RP14
RP13
RP12
RP11
RP10
RP9
RP8
…
022Eh
022Fh
RP55
RP63
RP54
RP62
RP53
RP61
RP52
RP60
RP51
RP59
RP50
RP58
RP49
RP57
RP48
RP56
Note: There is only write access to this register. Attempting to read the password reports all zeros. The password cannot be
changed while a mission is in progress.
Full Access Password Register
ADDRESS
0230h
0231h
…
BIT 7
FP7
BIT 6
FP6
BIT 5
FP5
BIT 4
FP4
BIT 3
FP3
BIT 2
FP2
BIT 1
FP1
BIT 0
FP0
FP15
FP14
FP13
FP12
FP11
FP10
FP9
FP8
…
0236h
0237h
FP55
FP63
FP54
FP62
FP53
FP61
FP52
FP60
FP51
FP59
FP50
FP58
FP49
FP57
FP48
FP56
Note: There is only write access to this register. Attempting to read the password reports all zeros. The password cannot be
changed while a mission is in progress.
Before enabling password checking, passwords for
read-only access as well as for full access
(read/write/control) must be written to the password
registers. Setting up a password or enabling/dis-
abling the password checking is done in the same
way as writing data to a memory location; only the
address is different. Since they are located in the
same memory page, both passwords can be rede-
fined at the same time.
The Full Access Password must be transmitted exactly
in the sequence FP0, FP1…FP62, FP63. It affects the
functions Read Memory with CRC, Copy Scratchpad,
Clear Memory, Start Mission, and Stop Mission. The
DS1922E executes the command only if the password
transmitted by the master was correct or if password
checking is not enabled.
Due to the special behavior of the write-access logic,
the Password Control register and both passwords
must be written at the same time. When setting up new
passwords, always verify (read back) the scratchpad
before sending the Copy Scratchpad command. After a
new password is successfully copied from the scratch-
pad to its memory location, erase the scratchpad by fill-
ing it with new data (Write Scratchpad command).
Otherwise, a copy of the passwords remains in the
scratchpad for public read access.
The Read Access Password must be transmitted exact-
ly in the sequence RP0, RP1…RP62, RP63. This pass-
word only applies to the Read Memory with CRC
function. The DS1922E delivers the requested data only
if the password transmitted by the master was correct
or if password checking is not enabled.
______________________________________________________________________________________ 19
High-Temperature Logger iButton with 8KB
Data-Log Memory
alarm flags must be cleared using the Memory Clear
command. To enable the device for a mission, the ETL
bit must be set to 1. These are general settings that
must be made in any case, regardless of the type of
object to be monitored and the duration of the mission.
ETL = 1
TLFS = 0
ETL = 1
TLFS = 1
1000h
1000h
WITH 16-BIT FORMAT,
If alarm signaling is desired, the temperature alarm low
and high thresholds must be defined. See the
Temperature Conversion section for how to convert a
temperature value into the binary code to be written to
the threshold registers. In addition, the temperature
alarm must be enabled for the low and/or high thresh-
old. This makes the device respond to a Conditional
Search command (see the1-Wire ROM Function
Commands section), provided that an alarming condi-
tion has been encountered.
THE MOST SIGNIFICANT
BYTE IS STORED AT THE
LOWER ADDRESS.
8192
8-BIT ENTRIES
4096
16-BIT ENTRIES
DS192E
2FFFh
2FFFh
Figure 7. Temperature Logging
Data-Log Memory Usage
The setting of the RO bit (rollover enable) and sample
rate depends on the duration of the mission and the
monitoring requirements. If the most recently logged
data is important, the rollover should be enabled (RO =
1). Otherwise, one should estimate the duration of the
mission in minutes and divide the number by 8192
(8-bit format) or 4096 (16-bit format) to calculate the
value of the sample rate (number of minutes between
conversions). For example, if the estimated duration of
a mission is 10 days (= 14400min), the 8192-byte
capacity of the data-log memory would be sufficient to
store a new 8-bit value every 1.8min (110s). If the
DS1922E’s data-log memory is not large enough to
store all readings, one can use several devices and set
the mission start delay to values that make the second
device start logging as soon as the memory of the first
device is full, and so on. The RO bit must be set to 0 to
disable rollover that would otherwise overwrite the
logged data.
Once set up for a mission, the DS1922E logs the temper-
ature measurements at equidistant time points entry after
entry in its data-log memory. The data-log memory can
store 8192 entries in 8-bit format or 4096 entries in 16-bit
format (Figure 7). In 16-bit format, the higher 8 bits of an
entry are stored at the lower address. Knowing the start-
ing time point (Mission Timestamp) and the interval
between temperature measurements, one can recon-
struct the time and date of each measurement.
There are two alternatives to the way the DS1922E
behaves after the data-log memory is filled with data. The
user can program the device to either stop any further
recording (disable rollover) or overwrite the previously
recorded data (enable rollover), one entry at a time, start-
ing again at the beginning of the respective memory sec-
tion. The contents of the Mission Samples Counter in
conjunction with the sample rate and the Mission
Timestamp allow reconstructing the time points of all val-
ues stored in the data-log memory. This gives the exact
history over time for the most recent measurements
taken. Earlier measurements cannot be reconstructed.
After the RO bit and the mission start delay are set, the
sample rate must be written to the Sample Rate regis-
ter. The sample rate can be any value from 1 to 16,383,
coded as an unsigned 14-bit binary number. The
fastest sample rate is one sample per second (EHSS =
1, sample rate = 0001h) and the slowest is one sample
every 273.05hr (EHSS = 0, sample rate = 3FFFh). To
get one sample every 6min, for example, the sample
rate value must be set to 6 (EHSS = 0) or 360 decimal
(equivalent to 0168h at EHSS = 1).
Missioning
The typical task of the DS1922E iButton is recording
temperature. Before the device can perform this func-
tion, it needs to be set up properly. This procedure is
called missioning.
First, the DS1922E must have its RTC set to a valid time
and date. This reference time can be the local time, or,
when used inside of a mobile unit, UTC (also called
GMT, Greenwich Mean Time), or any other time stan-
dard that was agreed upon. The RTC oscillator must be
running (EOSC = 1). The memory assigned to store the
mission timestamp, mission samples counter, and
If there is a risk of unauthorized access to the DS1922E
or manipulation of data, one should define passwords
for read access and full access. Before the passwords
become effective, their use must be enabled. See the
Security by Password section for more details.
20 ______________________________________________________________________________________
High-Temperature Logger iButton with 8KB
Data-Log Memory
DS192E
The last step to begin a mission is to issue the Start
Mission command. As soon as it has received this com-
mand, the DS1922E sets the MIP flag and clears the
MEMCLR flag. With the Immediate/Delayed Start Mode
(SUTA = 0), after as many minutes as specified by the
mission start delay are over, the device wakes up,
copies the current date and time to the Mission
Timestamp register, and logs the first entry of the mis-
sion. This increments both the mission samples counter
and device samples counter. All subsequent log entries
are made as specified by the value in the Sample Rate
register and the EHSS bit.
at any time, e.g., to watch the progress of a mission.
Attempts to read the passwords read 00h bytes instead
of the data that is stored in the password registers.
Memory Access
Address Registers and Transfer Status
Because of the serial data transfer, the DS1922E
employs three address registers called TA1, TA2, and
E/S (Figure 8). Registers TA1 and TA2 must be loaded
with the target address to which the data is written or
from which data is sent to the master upon a Read
command. Register E/S acts like a byte counter and
transfer status register. It is used to verify data integrity
with Write commands. Therefore, the master only has
read access to this register. The lower 5 bits of the E/S
register indicate the address of the last byte that has
been written to the scratchpad. This address is called
ending offset. The DS1922E requires that the ending
offset is always 1Fh for a Copy Scratchpad to func-
tion. Bit 5 of the E/S register, called PF or partial byte
flag, is set if the number of data bits sent by the master
is not an integer multiple of 8. Bit 6 is always a 0. Note
that the lowest 5 bits of the target address also deter-
mine the address within the scratchpad, where interme-
diate storage of data begins. This address is called
byte offset. If the target address for a Write command is
13Ch, for example, the scratchpad stores incoming
data beginning at the byte offset 1Ch and is full after
only 4 bytes. The corresponding ending offset in this
example is 1Fh. For best economy of speed and
If the Start Upon Temperature Alarm mode is chosen
(SUTA = 1) and temperature logging is enabled (ETL =
1), the DS1922E first waits until the start delay is over.
Then the device wakes up in intervals as specified by
the sample rate and EHSS bit and measures the tem-
perature. This increments the Device Samples Counter
register only. The first sample of the mission is logged
when the temperature alarm occurred. However, the
Mission Sample Counter does not increment. One sam-
ple period later the Mission Timestamp register is set.
From then on, both the Mission Samples Counter and
Device Samples Counter registers increment at the
same time. All subsequent log entries are made as
specified by the value in the Sample Rate register and
the EHSS bit.
The general-purpose memory operates independently of
the other memory sections and is not write protected
during a mission. All the DS1922E’s memory can be read
BIT NUMBER
7
6
5
4
3
2
1
0
TARGET ADDRESS (TA1)
T7
T6
T5
T4
T3
T2
T1
T0
TARGET ADDRESS (TA2)
T15
AA
T14
0
T13
PF
T12
E4
T11
E3
T10
E2
T9
E1
T8
E0
ENDING ADDRESS WITH
DATA STATUS (E/S)
(READ ONLY)
Figure 8. Address Registers
______________________________________________________________________________________ 21
High-Temperature Logger iButton with 8KB
Data-Log Memory
efficiency, the target address for writing should point to
Memory and Control
Function Commands
the beginning of a page, i.e., the byte offset is 0. Thus,
the full 32-byte capacity of the scratchpad is available,
resulting also in the ending offset of 1Fh. The ending
offset together with the PF flag are a means to support
the master checking the data integrity after a Write
command. The highest valued bit of the E/S register,
called authorization accepted (AA), indicates that a
valid Copy command for the scratchpad has been
received and executed. Writing data to the scratchpad
clears this flag.
Figure 9 shows the protocols necessary for accessing
the memory and the special function registers of the
DS1922E. An example on how to use these and other
functions to set up the DS1922E for a mission is includ-
ed in the Mission Example: Prepare and Start a New
Mission section. The communication between the mas-
ter and the DS1922E takes place either at standard
speed (default, OD = 0) or at overdrive speed (OD =
1). If not explicitly set into the Overdrive Mode the
DS1922E assumes standard speed. Internal memory
access during a mission has priority over external
access through the 1-Wire interface. This affects sever-
al commands in this section. See the Memory Access
Conflicts section for details and solutions.
DS192E
Writing with Verification
To write data to the DS1922E, the scratchpad must be
used as intermediate storage. First, the master issues
the Write Scratchpad command to specify the desired
target address, followed by the data to be written to the
scratchpad. In the next step, the master sends the
Read Scratchpad command to read the scratchpad
and to verify data integrity. As preamble to the scratch-
pad data, the DS1922E sends the requested target
address TA1 and TA2 and the contents of the E/S
Register. If the PF flag is set, data did not arrive cor-
rectly in the scratchpad. The master does not need to
continue reading; it can start a new trial to write data to
the scratchpad. Similarly, a set AA flag indicates that
the Write command was not recognized by the device.
If everything went correctly, both flags are cleared and
the ending offset indicates the address of the last byte
written to the scratchpad. Now the master can continue
verifying every data bit. After the master has verified
the data, it must send the Copy Scratchpad command.
This command must be followed exactly by the data of
the three address registers TA1, TA2, and E/S, as the
master has read them verifying the scratchpad. As
soon as the DS1922E has received these bytes, it
copies the data to the requested location beginning at
the target address.
Write Scratchpad Command [0Fh]
After issuing the Write Scratchpad command, the mas-
ter must first provide the 2-byte target address, fol-
lowed by the data to be written to the scratchpad. The
data is written to the scratchpad starting at the byte off-
set T[4:0]. The master must send as many bytes as are
needed to reach the ending offset of 1Fh. If a data byte
is incomplete, its content is ignored and the partial byte
flag PF is set.
When executing the Write Scratchpad command, the
CRC generator inside the DS1922E calculates a CRC
of the entire data stream, starting at the command code
and ending at the last data byte sent by the master
(Figure 15). This CRC is generated using the CRC-16
polynomial by first clearing the CRC generator and then
shifting in the command code (0Fh) of the Write
Scratchpad command, the target addresses TA1 and
TA2 as supplied by the master, and all the data bytes.
If the ending offset is 11111b, the master can send 16
read time slots and receive the inverted CRC-16 gener-
ated by the DS1922E.
Note that both register pages are write protected dur-
ing a mission. Although the Write Scratchpad com-
mand works normally at any time, the subsequent copy
scratchpad to a register page fails during a mission.
22 ______________________________________________________________________________________
High-Temperature Logger iButton with 8KB
Data-Log Memory
DS192E
progress, write attempts to the register pages are not
successful. The AA bit remaining at 0 indicates this.
Read Scratchpad Command [AAh]
This command is used to verify scratchpad data and
target address. After issuing the Read Scratchpad
command, the master begins reading. The first 2 bytes
are the target address. The next byte is the ending off-
set/data status byte (E/S) followed by the scratchpad
data beginning at the byte offset T[4:0], as shown in
Figure 8. The master can continue reading data until
the end of the scratchpad after which it receives an
inverted CRC-16 of the command code, target
addresses TA1 and TA2, the E/S byte, and the scratch-
pad data starting at the target address. After the CRC
is read, the bus master reads logic 1s from the
DS1922E until a reset pulse is issued.
Read Memory with Password and CRC
[69h]
The Read Memory with CRC command is the general
function to read from the device. This command gener-
ates and transmits a 16-bit CRC following the last data
byte of a memory page.
After having sent the command code of the Read
Memory with CRC command, the bus master sends a
2-byte address that indicates a starting byte location.
Next, the master must transmit one of the 64-bit pass-
words. If passwords are enabled and the transmitted
password does not match one of the stored passwords,
the Read Memory with Password and CRC command
fails. The device stops communicating and waits for a
reset pulse. If the password was correct or if pass-
words were not enabled, the master reads data from
the DS1922E beginning from the starting address and
continuing until the end of a 32-byte page is reached.
At that point the bus master sends 16 additional read
data time slots and receives the inverted 16-bit CRC.
With subsequent read data time slots the master
receives data starting at the beginning of the next
memory page followed again by the CRC for that page.
This sequence continues until the bus master resets the
device. When trying to read the passwords or memory
areas that are marked as “reserved,” the DS1922E
transmits 00h or FFh bytes, respectively. The CRC at
the end of a 32-byte memory page is based on the
data as it was transmitted.
Copy Scratchpad with Password [99h]
This command is used to copy data from the scratch-
pad to the writable memory sections. After issuing the
Copy Scratchpad command, the master must provide a
3-byte authorization pattern, which can be obtained by
reading the scratchpad for verification. This pattern
must exactly match the data contained in the three
address registers (TA1, TA2, E/S, in that order). Next,
the master must transmit the 64-bit full-access pass-
word. If passwords are enabled and the transmitted
password is different from the stored full-access pass-
word, the Copy Scratchpad with Password command
fails. The device stops communicating and waits for a
reset pulse. If the password was correct or if pass-
words were not enabled, the device tests the 3-byte
authorization code. If the authorization code pattern
matches, the AA flag is set and the copy begins. A pat-
tern of alternating 1s and 0s is transmitted after the
data has been copied until the master issues a reset
pulse. While the copy is in progress, any attempt to
reset the part is ignored. Copy typically takes 2µs per
byte.
With the initial pass through the Read Memory with
CRC flow, the 16-bit CRC value is the result of shifting
the command byte into the cleared CRC generator fol-
lowed by the two address bytes and the contents of the
data memory. Subsequent passes through the Read
Memory with CRC flow generate a 16-bit CRC that is
the result of clearing the CRC generator and then shift-
ing in the contents of the data memory page. After the
16-bit CRC of the last page is read, the bus master
receives logic 1s from the DS1922E until a reset pulse
is issued. The Read Memory with CRC command
sequence can be ended at any point by issuing a reset
pulse.
The data to be copied is determined by the three
address registers. The scratchpad data from the begin-
ning offset through the ending offset are copied, start-
ing at the target address. The AA flag remains at logic
1 until it is cleared by the next Write Scratchpad com-
mand. With suitable password, the copy scratchpad
always functions for the 16 pages of data memory and
the 2 pages of calibration memory. While a mission is in
______________________________________________________________________________________ 23
High-Temperature Logger iButton with 8KB
Data-Log Memory
MASTER Tx MEMORY OR
CONTROL FUNCTION COMMAND
FROM ROM FUNCTIONS
FLOWCHART (FIGURE 11)
99h
TO FIGURE 9b
0Fh
AAh
N
N
N
COPY SCRATCHPAD
[WITH PW]
WRITE SCRATCHPAD?
READ SCRATCHPAD?
Y
Y
Y
MASTER Tx
TA1 [T7:T0]
MASTER Rx
TA1 [T7:T0]
MASTER Tx
TA1 [T7:T0], TA2 [T15:T8]
DS192E
AUTHORIZATION
CODE
MASTER Tx
TA2 [T15:T8]
MASTER Rx
TA2 [T15:T8]
MASTER Tx
E/S BYTE
DS1922E SETS
SCRATCHPAD OFFSET = [T4:T0]
AND CLEARS (PF, AA)
MASTER Rx ENDING OFFSET
WITH DATA STATUS
(E/S)
MASTER Tx
64 BITS [PASSWORD]
N
N
PASSWORD
ACCEPTED?
MASTER Tx DATA BYTE
TO SCRATCHPAD OFFSET
DS1922E SETS
SCRATCHPAD OFFSET = [T4:T0]
Y
DS1922E
INCREMENTS
SCRATCHPAD
OFFSET
DS1922E SETS [E4:E0] =
SCRATCHPAD OFFSET
DS1922E
INCREMENTS
SCRATCHPAD
OFFSET
MASTER Rx DATA BYTE FROM
SCRATCHPAD OFFSET
AUTHORIZATION
CODE MATCH?
Y
Y
Y
MASTER Tx RESET?
N
MASTER Tx RESET?
N
AA = 1
DS1922E COPIES SCRATCHPAD
DATA TO MEMORY
N
Y
SCRATCHPAD
OFFSET = 11111b?
N
SCRATCHPAD
OFFSET = 11111b?
PARTIAL
BYTE WRITTEN?
Y
Y
Y
MASTER Rx "1"s
MASTER Rx "1"s
N
COPYING
FINISHED
MASTER Rx CRC-16 OF
COMMAND, ADDRESS DATA,
E/S BYTE, AND DATA STARTING
AT THE TARGET ADDRESS
N
MASTER Tx RESET?
N
N
Y
MASTER Tx RESET?
Y
PF = 1
DS1922E Tx "0"
MASTER Rx CRC-16 OF
COMMAND, ADDRESS DATA
Y
MASTER Tx RESET?
Y
MASTER Tx RESET?
N
Y
MASTER Tx RESET?
MASTER Rx "1"s
N
N
DS1922E Tx "1"
MASTER Rx "1"s
N
MASTER Tx RESET?
Y
FROM FIGURE 9b
TO ROM FUNCTIONS
FLOWCHART (FIGURE 11)
Figure 9a. Memory/Control Function Flowchart
24 ______________________________________________________________________________________
High-Temperature Logger iButton with 8KB
Data-Log Memory
DS192E
69h
96h
FROM FIGURE 9a
TO FIGURE 9c
55h
N
N
N
READ MEMORY [WITH
PW] AND CRC
CLEAR MEMORY
[WITH PW]
FORCED CONVERSION?
Y
Y
Y
MASTER Tx
MASTER Tx
MASTER Tx
TA1 [T7:T0], TA2 [T15:T8]
64 BITS [PASSWORD]
FFh DUMMY BYTE
MASTER Tx
64 BITS [PASSWORD]
MASTER Tx
FFh DUMMY BYTE
Y
MISSION IN
PROGRESS?
DECISION MADE
BY DS1922E
N
N
N
Y
PASSWORD
ACCEPTED?
PASSWORD
ACCEPTED?
DS1922E PERFORMS A
TEMPERATURE CONVERSION
Y
Y
DECISION MADE
BY MASTER
DS1922E SETS
MEMORY ADDRESS = [T15:T0]
DS1922E COPIES RESULT TO
ADDRESS 020C/Dh
MISSION IN
PROGRESS?
N
MASTER Rx DATA BYTE FROM
MEMORY ADDRESS
N
MASTER Tx RESET?
Y
DS1922E CLEARS
MISSION TIMESTAMP,
MISSION SAMPLES COUNTER,
ALARM FLAGS
DS1922E
INCREMENTS
ADDRESS
Y
MASTER Tx RESET?
N
COUNTER
DS1922E SETS
MEMCLR = 1
N
END OF PAGE?
Y
N
MASTER Tx RESET?
Y
MASTER Rx CRC-16 OF
COMMAND, ADDRESS, DATA
(1ST PASS); CRC-16 OF DATA
(SUBSEQUENT PASSES)
N
MASTER Tx RESET
CRC OK?
Y
N
N
END OF MEMORY?
Y
MASTER Rx "1"s
MASTER Tx RESET?
Y
TO FIGURE 9a
FROM FIGURE 9c
Figure 9b. Memory/Control Function Flowchart (continued)
______________________________________________________________________________________ 25
High-Temperature Logger iButton with 8KB
Data-Log Memory
CCh
START MISSION
[WITH PW]
33h
FROM FIGURE 9b
N
N
STOP MISSION
[WITH PW]
MISSION START
DELAY PROCESS
Y
Y
MASTER Tx
MASTER Tx
DS192E
64 BITS [PASSWORD]
64 BITS [PASSWORD]
Y
START DELAY
COUNTER = 0?
MASTER Tx
FFh DUMMY BYTE
MASTER Tx
FFh DUMMY BYTE
N
DS1922E WAITS FOR 1 MINUTE
N
Y
N
N
N
PASSWORD
ACCEPTED?
PASSWORD
ACCEPTED?
DS1922E DECREMENTS
START DELAY COUNTER
Y
Y
MISSION IN
PROGRESS?
MISSION IN
PROGRESS?
N
SUTA = 1?
N
Y
Y
DS1922E SETS WFTA = 1
DS1922E SETS
MIP = 0,
WFTA = 0
MEMCLR = 1?
Y
DS1922E WAITS ONE
SAMPLE PERIOD
DS1922E SETS
MIP = 1,
MEMCLR = 0
N
Y
MASTER Tx RESET?
Y
MIP = 0?
N
DS1922E INITIATES MISSION
START DELAY PROCESS
DS1922E PERFORMS 8-BIT
TEMPERATURE CONVERSION
N
MASTER Tx RESET?
Y
N
TEMPERATURE
ALARM?
Y
DS1922E SETS WFTA = 0
DS1922E WAITS ONE
SAMPLE PERIOD
DS1922E COPIES RTC DATA TO
MISSION TIMESTAMP REGISTER
DS1922E STARTS LOGGING
TAKING FIRST SAMPLE
END OF PROCESS
TO FIGURE 9b
Figure 9c. Memory/Control Function Flowchart (continued)
26 ______________________________________________________________________________________
High-Temperature Logger iButton with 8KB
Data-Log Memory
DS192E
Clear Memory with Password [96h]
The Clear Memory with Password command is used to
prepare the device for another mission. This command
is only executed if no mission is in progress. After the
command code the master must transmit the 64-bit full-
access password followed by an FFh dummy byte. If
passwords are enabled and the transmitted password
is different from the stored full-access password or a
mission is in progress, the Clear Memory with
Password command fails. The device stops communi-
cating and waits for a reset pulse. If the password was
correct or if passwords were not enabled, the device
clears the Mission Timestamp register, Mission
Samples Counter register, and all alarm flags of the
Alarm Status register. After these cells are cleared, the
MEMCLR bit of the General Status register reads 1 to
indicate the successful execution of the Clear Memory
with Password command. Clearing of the data-log
memory is not necessary because the mission samples
counter indicates how many entries in the data-log
memory are valid.
Start Mission with Password [CCh]
The DS1922E uses a control function command to start
a mission. A new mission can only be started if the pre-
vious mission has been ended and the memory has
been cleared. After the command code, the master
must transmit the 64-bit full-access password followed
by an FFh dummy byte. If passwords are enabled and
the transmitted password is different from the stored
full-access password or a mission is in progress, the
Start Mission with Password command fails. The device
stops communicating and waits for a reset pulse. If the
password was correct or if passwords were not
enabled, the device starts a mission. If SUTA = 0, the
sampling begins as soon as the mission start delay is
over. If SUTA = 1, the first sample is written to the data-
log memory at the time the temperature alarm
occurred. However, the mission sample counter does
not increment. One sample period later, the Mission
Timestamp register is set and the regular sampling and
logging begins. While the device is waiting for a tem-
perature alarm to occur, the WFTA flag in the General
Status register reads 1. During a mission there is only
read access to the register pages.
Forced Conversion [55h]
The Forced Conversion command can be used to mea-
sure the temperature without starting a mission. After
the command code, the master must send one FFh
byte to get the conversion started. The conversion
result is found as a 16-bit value in the Latest
Temperature Conversion Result register. This com-
mand is only executed if no mission is in progress (MIP
= 0). It cannot be interrupted and takes maximum
600ms to complete. During this time memory access
through the 1-Wire interface is blocked. The device
behaves the same way as during a mission when the
sampling interferes with a memory/control function
command. See the Memory Access Conflicts section
for details.
Stop Mission with Password [33h]
The DS1922E uses a control function command to stop
a mission. Only a mission that is in progress can be
stopped. After the command code, the master must
transmit the 64-bit full-access password followed by a
FFh dummy byte. If passwords are enabled and the
transmitted password is different from the stored full-
access password or a mission is not in progress, the
Stop Mission with Password command fails. The device
stops communicating and waits for a reset pulse. If the
password was correct or if passwords were not
enabled, the device clears the MIP bit in the General
Status register and restores write access to the register
pages. The WFTA bit is not cleared. See the descrip-
tion of the General Status register for a method to clear
the WFTA bit.
______________________________________________________________________________________ 2±
High-Temperature Logger iButton with 8KB
Data-Log Memory
mission is in progress or while the device is waiting for
Memory Access Conflicts
a temperature alarm. Table 3 explains how the remain-
While a mission is in progress or while the device is
ing five commands are affected by internal activity, how
to detect this interference, and how to work around it.
waiting for a temperature alarm to start a mission, peri-
odically a temperature sample is taken and logged.
The interference is more likely to be seen with a high-
sample rate (one sample every second) and with high-
resolution logging, which can last up to 600ms. With
lower sample rates, interference may hardly be visible
at all. In any case, when writing driver software it is
important to know about the possibility of interference
and to take measures to work around it.
This “internal activity” has priority over 1-Wire communi-
cation. As a consequence, device-specific commands
(excluding ROM function commands and 1-Wire reset)
do not perform properly when internal and “external”
activities interfere with each other. Not affected are the
commands Start Mission, Forced Conversion, and
Clear Memory, because they are not applicable while a
DS192E
Table 3. Memory Access Conflicts and Solutions
COMMAND
INDICATION OF INTERFERENCE
SOLUTION
Wait 0.5s, 1-Wire reset, address the device, repeat
Write Scratchpad with the same data, and check the
validity of the CRC-16 at the end of the command
flow. Alternatively, use Read Scratchpad to verify
data integrity.
The CRC-16 at the end of the command flow reads
FFFFh.
Write Scratchpad
The data read changes to FFh bytes or all bytes
received are FFh, including the CRC at the end of
the command flow.
Wait 0.5s, 1-Wire reset, address the device, repeat
Read Scratchpad, and check the validity of the
CRC-16 at the end of the command flow.
Read Scratchpad
Copy Scratchpad
Wait 0.5s, 1-Wire reset, address the device, issue
Read Scratchpad, and check the AA bit of the E/S
byte. If the AA bit is set, Copy Scratchpad was
successful.
The device behaves as if the authorization code or
password was not valid, or as if the copy function
would not end.
The data read changes to all FFh bytes or all bytes
received are FFh, including the CRC at the end of
the command flow, despite a valid password.
Wait 0.5s, 1-Wire reset, address the device, repeat
Read Memory with CRC, and check the validity of
the CRC-16 at the end of the memory page.
Read Memory with
CRC
Wait 0.5s, 1-Wire reset, address the device, and
repeat Stop Mission. Perform a 1-Wire reset, address
the device, read the General Status register at
address 0215h, and check the MIP bit. If the MIP bit
is 0, Stop Mission was successful.
The General Status register at address 0215h reads
FFh or the MIP bit is 1 while bits 0, 2, and 5 are 0.
Stop Mission
28 ______________________________________________________________________________________
High-Temperature Logger iButton with 8KB
Data-Log Memory
DS192E
The value of the pullup resistor primarily depends on
1-Wire Bus System
the network size and load conditions. The DS1922E
The 1-Wire bus is a system that has a single bus mas-
requires a pullup resistor of maximum 2.2kΩ at any
ter and one or more slaves. In all instances the
speed.
DS1922E is a slave device. The bus master is typically
The idle state for the 1-Wire bus is high. If for any rea-
son a transaction needs to be suspended, the bus
must be left in the idle state if the transaction is to
resume. If this does not occur and the bus is left low for
more than 16µs (overdrive speed) or more than 120µs
(standard speed), one or more devices on the bus may
be reset. Note that the DS1922E does not quite meet
the full 16µs maximum low time of the normal 1-Wire
bus overdrive timing. With the DS1922E the bus must
be left low for no longer than 12µs at overdrive to
ensure that no DS1922E on the 1-Wire bus performs a
reset. The DS1922E communicates properly when used
in conjunction with a DS2480B or DS2490 1-Wire driver
and adapters that are based on these driver chips.
a microcontroller. The discussion of this bus system is
broken down into three topics: hardware configuration,
transaction sequence, and 1-Wire signaling (signal
types and timing). The 1-Wire protocol defines bus
transactions in terms of the bus state during specific
time slots that are initiated on the falling edge of sync
pulses from the bus master.
Hardware Configuration
The 1-Wire bus has only a single line by definition; it is
important that each device on the bus be able to drive
it at the appropriate time. To facilitate this, each device
attached to the 1-Wire bus must have open-drain or
three-state outputs. The 1-Wire port of the DS1922E is
open drain with an internal circuit equivalent to that
shown in Figure 10.
Transaction Sequence
The protocol for accessing the DS1922E through the
1-Wire port is as follows:
A multidrop bus consists of a 1-Wire bus with multiple
slaves attached. At standard speed the 1-Wire bus has
a maximum data rate of 16.3kbps. The speed can be
boosted to 142kbps by activating the Overdrive Mode.
The DS1922E is not guaranteed to be fully compliant to
the iButton standard. Its maximum data rate in standard
speed is 15.4kbps and 125kbps in overdrive speed.
• Initialization
• ROM Function Command
• Memory/Control Function Command
• Transaction/Data
V
PUP
BUS MASTER
DS1922E 1-Wire PORT
R
PUP
DATA
Rx
Tx
Rx
I
Tx
L
Rx = RECEIVE
Tx = TRANSMIT
OPEN-DRAIN
PORT PIN
100Ω MOSFET
Figure 10. Hardware Configuration
______________________________________________________________________________________ 29
High-Temperature Logger iButton with 8KB
Data-Log Memory
numbers of all slave devices. For each bit of the regis-
Initialization
tration number, starting with the least significant bit, the
All transactions on the 1-Wire bus begin with an initial-
bus master issues a triplet of time slots. On the first slot,
ization sequence. The initialization sequence consists
each slave device participating in the search outputs
of a reset pulse transmitted by the bus master followed
the true value of its registration number bit. On the sec-
by presence pulse(s) transmitted by the slave(s). The
ond slot, each slave device participating in the search
presence pulse lets the bus master know that the
outputs the complemented value of its registration num-
DS1922E is on the bus and is ready to operate. For
ber bit. On the third slot, the master writes the true
more details, see the 1-Wire Signaling section.
value of the bit to be selected. All slave devices that do
not match the bit written by the master stop participat-
DS192E
1-Wire ROM Function Commands
ing in the search. If both of the read bits are zero, the
Once the bus master has detected a presence, it can
master knows that slave devices exist with both states
issue one of the eight ROM function commands that the
of the bit. By choosing which state to write, the bus
DS1922E supports. All ROM function commands are 8
master branches in the ROM code tree. After one com-
bits long. A list of these commands follows (see the
plete pass, the bus master knows the registration num-
flowchart in Figure 11).
ber of a single device. Additional passes identify the
registration numbers of the remaining devices. Refer to
Read ROM [33h]
Application Note 187: 1-Wire Search Algorithm for a
detailed discussion, including an example.
This command allows the bus master to read the
DS1922E’s 8-bit family code, unique 48-bit serial number,
and 8-bit CRC. This command can only be used if there
is a single slave on the bus. If more than one slave is pre-
sent on the bus, a data collision occurs when all slaves
try to transmit at the same time (open drain produces a
wired-AND result). The resultant family code and 48-bit
serial number results in a mismatch of the CRC.
Conditional Search ROM [ECh]
The Conditional Search ROM command operates simi-
larly to the Search ROM command except that only
those devices that fulfill certain conditions participate in
the search. This function provides an efficient means
for the bus master to identify devices on a multidrop
system that have to signal an important event. After
each pass of the conditional search that successfully
determined the 64-bit ROM code for a specific device
on the multidrop bus, that particular device can be indi-
vidually accessed as if a Match ROM had been issued,
since all other devices have dropped out of the search
process and are waiting for a reset pulse.
Match ROM [55h]
The Match ROM command, followed by a 64-bit ROM
sequence, allows the bus master to address a specific
DS1922E on a multidrop bus. Only the DS1922E that
exactly matches the 64-bit ROM sequence responds to
the following memory function command. All other slaves
wait for a reset pulse. This command can be used with a
single device or multiple devices on the bus.
The DS1922E responds to the Conditional Search ROM
command if one of the three alarm flags of the Alarm
Status register (address 0214h) reads 1. The tempera-
ture alarm only occurs if enabled (see the Temperature
Sensor Alarm section). The BOR alarm is always
enabled. The first alarm that occurs makes the device
respond to the Conditional Search ROM command.
Search ROM [F0h]
When a system is initially brought up, the bus master
might not know the number of devices on the 1-Wire
bus or their registration numbers. By taking advantage
of the wired-AND property of the bus, the master can
use a process of elimination to identify the registration
30 ______________________________________________________________________________________
High-Temperature Logger iButton with 8KB
Data-Log Memory
DS192E
Skip ROM command sets the DS1922E in the Overdrive
Mode (OD = 1). All communication following this com-
mand must occur at overdrive speed until a reset pulse
of minimum 690µs duration resets all devices on the
bus to standard speed (OD = 0).
Skip ROM [CCh]
This command can save time in a single-drop bus sys-
tem by allowing the bus master to access the memory
functions without providing the 64-bit ROM code. For
example, if more than one slave is present on the bus
and a Read command is issued following the Skip ROM
command, data collision occurs on the bus as multiple
slaves transmit simultaneously (open-drain pulldowns
produce a wired-AND result).
When issued on a multidrop bus, this command sets all
overdrive-supporting devices into Overdrive Mode. To
subsequently address a specific overdrive-supporting
device, a reset pulse at overdrive speed must be
issued followed by a Match ROM or Search ROM com-
mand sequence. This speeds up the time for the
search process. If more than one slave supporting
overdrive is present on the bus and the Overdrive-Skip
ROM command is followed by a Read command, data
collision occurs on the bus as multiple slaves transmit
simultaneously (open-drain pulldowns produce a wired-
AND result).
Resume [A5h]
The DS1922E must be accessed several times before a
mission starts. In a multidrop environment this means
that the 64-bit ROM code after a Match ROM command
must be repeated for every access. To maximize the
data throughput in a multidrop environment, the Resume
function was implemented. This function checks the sta-
tus of the RC bit and, if it is set, directly transfers control
to the memory/control functions, similar to a Skip ROM
command. The only way to set the RC bit is through
successfully executing the Match ROM, Search ROM, or
Overdrive-Match ROM command. Once the RC bit is
set, the device can repeatedly be accessed through the
Resume command function. Accessing another device
on the bus clears the RC bit, preventing two or more
devices from simultaneously responding to the Resume
command function.
Overdrive-Match ROM [69h]
The Overdrive-Match ROM command followed by a
64-bit ROM sequence transmitted at overdrive speed
allows the bus master to address a specific DS1922E
on a multidrop bus and to simultaneously set it in
Overdrive Mode. Only the DS1922E that exactly match-
es the 64-bit ROM sequence responds to the subse-
quent memory/control function command. Slaves
already in Overdrive Mode from a previous Overdrive-
Skip ROM or successful Overdrive-Match ROM com-
mand remain in Overdrive Mode. All overdrive-capable
slaves return to standard speed at the next reset pulse
of minimum 690µs duration. The Overdrive-Match ROM
command can be used with a single or multiple
devices on the bus.
Overdrive-Skip ROM [3Ch]
On a single-drop bus this command can save time by
allowing the bus master to access the memory/control
functions without providing the 64-bit ROM code.
Unlike the normal Skip ROM command, the Overdrive-
______________________________________________________________________________________ 31
High-Temperature Logger iButton with 8KB
Data-Log Memory
BUS MASTER Tx
RESET PULSE
FROM FIGURE 11b
FROM MEMORY FUNCTIONS
FLOWCHART (FIGURE 9)
OD
N
OD = 0
RESET PULSE?
Y
BUS MASTER Tx ROM
FUNCTION COMMAND
DS1922E Tx
PRESENCE PULSE
DS192E
33h
READ ROM
COMMAND?
55h
MATCH ROM
COMMAND?
F0h
SEARCH ROM
COMMAND?
ECh
TO FIGURE 11b
N
N
N
N
CONDITIONAL SEARCH
COMMAND?
Y
Y
Y
Y
RC = 0
RC = 0
RC = 0
RC = 0
N
N
N
CONDITION
MET?
Y
DS1922E Tx BIT 0
DS1922E Tx BIT 0
MASTER Tx BIT 0
DS1922E Tx BIT 0
DS1922E Tx BIT 0
MASTER Tx BIT 0
DS1922E Tx
FAMILY CODE
(1 BYTE)
MASTER Tx BIT 0
BIT 0 MATCH?
N
N
BIT 0 MATCH?
Y
BIT 0 MATCH?
Y
Y
DS1922E Tx BIT 1
DS1922E Tx BIT 1
MASTER Tx BIT 1
DS1922E Tx BIT 1
DS1922E Tx BIT 1
MASTER Tx BIT 1
DS1922E Tx
SERIAL NUMBER
(6 BYTES)
MASTER Tx BIT 1
N
N
BIT 1 MATCH?
Y
BIT 1 MATCH?
Y
BIT 1 MATCH?
Y
DS1922E Tx BIT 63
DS1922E Tx BIT 63
MASTER Tx BIT 63
DS1922E Tx BIT 63
DS1922E Tx BIT 63
MASTER Tx BIT 63
DS1922E Tx
CRC BYTE
MASTER Tx BIT 63
BIT 63 MATCH?
N
N
N
BIT 63 MATCH?
BIT 63 MATCH?
Y
Y
Y
RC = 1
RC = 1
RC = 1
TO FIGURE 11b
FROM FIGURE 11b
TO MEMORY FUNCTIONS
FLOWCHART (FIGURE 9)
Figure 11a. ROM Functions Flowchart
32 ______________________________________________________________________________________
High-Temperature Logger iButton with 8KB
Data-Log Memory
DS192E
TO FIGURE 11a
CCh
SKIP ROM
COMMAND?
A5h
RESUME
COMMAND?
3Ch
OVERDRIVE-
SKIP ROM?
69h
OVERDRIVE-
MATCH ROM?
FROM FIGURE 11a
N
N
N
N
Y
Y
Y
Y
RC = 0
RC = 0; OD = 1
RC = 0; OD = 1
N
RC = 1?
Y
Y
MASTER Tx
RESET?
MASTER Tx BIT 0
BIT 0 MATCH?
N
(SEE NOTE)
OD = 0
Y
N
N
N
MASTER Tx
RESET?
N
Y
MASTER Tx BIT 1
(SEE NOTE)
OD = 0
BIT 1 MATCH?
Y
MASTER Tx BIT 63
BIT 63 MATCH?
(SEE NOTE)
OD = 0
Y
RC = 1
FROM FIGURE 11a
TO FIGURE 11a
NOTE: THE OD FLAG REMAINS AT 1 IF THE DEVICE WAS ALREADY AT OVERDRIVE SPEED BEFORE THE OVERDRIVE-MATCH ROM COMMAND WAS ISSUED.
Figure 11b. ROM Functions Flowchart (continued)
______________________________________________________________________________________ 33
High-Temperature Logger iButton with 8KB
Data-Log Memory
DS1922E is in Overdrive Mode and t
is no longer
RSTL
1-Wire Signaling
than 80µs, the device remains in Overdrive Mode.
The DS1922E requires strict protocols to ensure data
integrity. The protocol consists of four types of signaling
on one line: reset sequence with reset pulse and pres-
ence pulse, write-zero, write-one, and read-data. Except
for the presence pulse, the bus master initiates all these
signals. The DS1922E can communicate at two different
speeds: standard speed and overdrive speed. If not
explicitly set into the Overdrive Mode, the DS1922E
communicates at standard speed. While in Overdrive
Mode the fast timing applies to all waveforms.
After the bus master has released the line, it goes into
receive mode (Rx). Now the 1-Wire bus is pulled to
PUP
V
through the pullup resistor or, in the case of a
DS2480B driver, through active circuitry. When the
threshold V is crossed, the DS1922E waits for t
TH
PDH
and then transmits a presence pulse by pulling the line
low for t . To detect a presence pulse, the master
DS192E
PDL
must test the logical state of the 1-Wire line at t
.
MSP
The t
window must be at least the sum of
RSTH
t
t
, t
, and t
. Immediately after
RECMIN
PDHMAX PDLMAX
RSTH
To get from idle to active, the voltage on the 1-Wire line
is expired, the DS1922E is ready for data com-
needs to fall from V
below the threshold V . To get
PUP
TL
munication. In a mixed population network, t
RSTH
from active to idle, the voltage needs to rise from V
IL-
should be extended to minimum 480µs at standard
speed and 48µs at overdrive speed to accommodate
other 1-Wire devices.
past the threshold V . The time it takes for the
MAX
TH
voltage to make this rise is seen in Figure 12 as “ε” and
its duration depends on the pullup resistor (R ) used
PUP
and the capacitance of the 1-Wire network attached.
Read/Write Time Slots
Data communication with the DS1922E takes place in
time slots that carry a single bit each. Write time slots
transport data from bus master to slave. Read time slots
transfer data from slave to master. The definitions of the
write and read time slots are illustrated in Figure 13.
The voltage V
is relevant for the DS1922E when
ILMAX
determining a logical level, not triggering any events.
The initialization sequence required to begin any com-
munication with the DS1922E is shown in Figure 12. A
reset pulse followed by a presence pulse indicates the
DS1922E is ready to receive data, given the correct
ROM and memory function command. If the bus master
uses slew-rate control on the falling edge, it must pull
All communication begins with the master pulling the
data line low. As the voltage on the 1-Wire line falls
below the threshold V , the DS1922E starts its internal
TL
timing generator that determines when the data line is
sampled during a write time slot and how long data is
valid during a read time slot.
down the line for t
+ t to compensate for the edge.
F
RSTL
A t
duration of 690µs or longer exits the Overdrive
RSTL
Mode, returning the device to standard speed. If the
MASTER Tx "RESET PULSE"
MASTER Rx "PRESENCE PULSE"
ε
t
MSP
V
PUP
V
IHMASTER
V
TH
V
TL
V
ILMAX
0V
t
PDH
t
t
t
REC
RSTL
PDL
t
F
t
RSTH
RESISTOR
MASTER
DS1922E
Figure 12. Initialization Procedure: Reset and Presence Pulse
34 ______________________________________________________________________________________
High-Temperature Logger iButton with 8KB
Data-Log Memory
DS192E
Master-to-Slave
points and branch points can add up or cancel each
other to some extent. Such reflections are visible as
glitches or ringing on the 1-Wire communication line.
Noise coupled onto the 1-Wire line from external
sources can also result in signal glitching. A glitch dur-
ing the rising edge of a time slot can cause a slave
device to lose synchronization with the master and, as
a consequence, result in a Search ROM command
coming to a dead end or cause a device-specific func-
tion command to abort. For better performance in net-
work applications, the DS1922E uses a new 1-Wire
front-end, which makes it less sensitive to noise and
also reduces the magnitude of noise injected by the
slave device itself.
For a write-one time slot, the voltage on the data line
must have crossed the V threshold before the write-one
TH
low time t
is expired. For a write-zero time slot,
W1LMAX
the voltage on the data line must stay below the V
TH
threshold until the write-zero low time t
is expired.
W0LMIN
The voltage on the data line should not exceed V
ILMAX
window. After the V
during the entire t
or t
W0L
W1L TH
threshold has been crossed, the DS1922E needs a
recovery time t
before it is ready for the next time slot.
REC
Slave-to-Master
A read-data time slot begins like a write-one time slot.
The voltage on the data line must remain below V
TL
until the read low time t
is expired. During the t
RL
RL
The DS1922E’s 1-Wire front-end differs from traditional
slave devices in four characteristics:
window, when responding with a 0, the DS1922E starts
pulling the data line low; its internal timing generator
determines when this pulldown ends and the voltage
starts rising again. When responding with a 1, the
DS1922E does not hold the data line low at all, and the
1) The falling edge of the presence pulse has a con-
trolled slew rate. This provides a better match to the
line impedance than a digitally switched transistor,
converting the high-frequency ringing known from
traditional devices into a smoother low-bandwidth
transition. The slew-rate control is specified by the
voltage starts rising as soon as t is over.
RL
The sum of t + δ (rise time) on one side and the inter-
nal timing generator of the DS1922E on the other side
RL
parameter t
, which has different values for stan-
FPD
define the master sampling window (t
to
MSRMIN
dard and overdrive speed.
t
) in which the master must perform a read from
MSRMAX
2) There is additional lowpass filtering in the circuit that
detects the falling edge at the beginning of a time
slot. This reduces the sensitivity to high-frequency
noise. This additional filtering does not apply at
overdrive speed.
the data line. For most reliable communication, t
RL
should be as short as permissible and the master
should read close to but no later than t . After
MSRMAX
reading from the data line, the master must wait until
is expired. This guarantees sufficient recovery
t
SLOT
time t
for the DS1922E to get ready for the next time
REC
3) There is a hysteresis at the low-to-high switching
slot. Note that t
specified herein applies only to a
REC
threshold V . If a negative glitch crosses V
but
TH
TH
single DS1922E attached to a 1-Wire line. For multiple
device configurations, t must be extended to
does not go below V
- V , it is not recognized
HY
TH
REC
(Figure 14, Case A). The hysteresis is effective at
any 1-Wire speed.
accommodate the additional 1-Wire device input
capacitance. Alternatively, an interface that performs
active pullup during the 1-Wire recovery time such as
the DS2482-x00 or DS2480B 1-Wire line drivers can be
used.
4) There is a time window specified by the rising edge
hold-off time t
during which glitches are ignored,
REH
even if they extend below V
- V
threshold
HY
TH
REH
(Figure 14, Case B, t
< t
). Deep voltage
GL
droops or glitches that appear late after crossing the
threshold and extend beyond the t window
Improved Network Behavior
(Switchpoint Hysteresis)
In a 1-Wire environment line termination is possible only
during transients controlled by the bus master (1-Wire
driver). 1-Wire networks, therefore, are susceptible to
noise of various origins. Depending on the physical
size and topology of the network, reflections from end
V
TH
REH
cannot be filtered out and are taken as the begin-
ning of a new time slot (Figure 14, Case C, t
≥
GL
t ).
REH
Devices that have the parameters t , V , and t
FPD HY REH
specified in their electrical characteristics use the
improved 1-Wire front-end.
______________________________________________________________________________________ 35
High-Temperature Logger iButton with 8KB
Data-Log Memory
WRITE-ONE TIME SLOT
t
W1L
V
PUP
V
IHMASTER
V
TH
V
TL
DS192E
V
ILMAX
0V
ε
t
F
t
SLOT
RESISTOR
MASTER
WRITE-ZERO TIME SLOT
t
W0L
V
PUP
V
IHMASTER
V
TH
V
TL
V
ILMAX
0V
ε
t
F
t
REC
t
SLOT
RESISTOR
MASTER
READ-DATA TIME SLOT
t
MSR
t
RL
V
PUP
V
IHMASTER
V
TH
MASTER
SAMPLING
WINDOW
V
TL
V
ILMAX
0V
δ
t
t
REC
F
t
SLOT
RESISTOR
MASTER
DS1922E
Figure 13. Read/Write Timing Diagrams
36 ______________________________________________________________________________________
High-Temperature Logger iButton with 8KB
Data-Log Memory
DS192E
t
REH
t
REH
V
PUP
V
TH
V
HY
CASE A
CASE B
CASE C
0V
t
GL
t
GL
Figure 14. Noise Suppression Scheme
16
15
2
POLYNOMIAL = X + X + X + 1
1ST
2ND
3RD
4TH
5TH
6TH
7TH
8TH
STAGE
STAGE
STAGE
STAGE
STAGE
STAGE
STAGE
STAGE
0
1
2
3
4
5
6
7
X
X
X
X
X
X
X
X
9TH
STAGE
10TH
STAGE
11TH
STAGE
12TH
STAGE
13TH
STAGE
14TH
STAGE
15TH
STAGE
16TH
STAGE
8
9
10
11
12
13
14
15
16
CRC OUTPUT
X
X
X
X
X
X
X
X
X
INPUT DATA
Figure 15. CRC-16 Hardware Description and Polynomial
16-bit CRC is always communicated in the inverted
form. A CRC generator inside the DS1922E (Figure 15)
calculates a new 16-bit CRC as shown in the command
flowchart of Figure 9. The bus master compares the
CRC value read from the device to the one it calculates
from the data and decides whether to continue with an
operation or to reread the portion of the data with the
CRC error. With the initial pass through the Read
Memory with CRC flowchart, the 16-bit CRC value is the
result of shifting the command byte into the cleared
CRC generator, followed by the two address bytes and
the data bytes. The password is excluded from the
CRC calculation. Subsequent passes through the Read
Memory with CRC flowchart generate a 16-bit CRC that
is the result of clearing the CRC generator and then
shifting in the data bytes.
CRC Generation
The DS1922E uses two types of CRCs. One CRC is an
8-bit type and is stored in the most significant byte of
the 64-bit ROM. The bus master can compute a CRC
value from the first 56 bits of the 64-bit ROM and com-
pare it to the value stored within the DS1922E to deter-
mine if the ROM data has been received error-free. The
equivalent polynomial function of this CRC is X8 + X5 +
X4 + 1. This 8-bit CRC is received in the true (noninvert-
ed) form, and it is computed at the factory and lasered
into the ROM.
The other CRC is a 16-bit type, generated according to
the standardized CRC-16 polynomial function x16 + x15
+ x2 + 1. This CRC is used for error detection when
reading register pages or the data-log memory using
the Read Memory with CRC command and for fast veri-
fication of a data transfer when writing to or reading
from the scratchpad. In contrast to the 8-bit CRC, the
With the Write Scratchpad command, the CRC is gener-
ated by first clearing the CRC generator and then shift-
______________________________________________________________________________________ 3±
High-Temperature Logger iButton with 8KB
Data-Log Memory
ing in the command code, the target addresses TA1
and TA2, and all the data bytes. The DS1922E transmits
this CRC only if the data bytes written to the scratchpad
include scratchpad ending offset 11111b. The data can
start at any location within the scratchpad.
shifting in the command code, the target addresses
TA1 and TA2, the E/S byte, and the scratchpad data
starting at the target address. The DS1922E transmits
this CRC only if the reading continues through the end
of the scratchpad, regardless of the actual ending off-
set. For more information on generating CRC values,
refer to Application Note 27.
With the Read Scratchpad command, the CRC is gen-
erated by first clearing the CRC generator and then
DS192E
Command-Specific 1-Wire Communication Protocol—Legend
SYMBOL
RST
DESCRIPTION
1-Wire reset pulse generated by master.
PD
1-Wire presence pulse generated by slave.
Command and data to satisfy the ROM function protocol.
Command "Write Scratchpad."
Select
WS
RS
Command "Read Scratchpad."
CPS
Command "Copy Scratchpad with Password."
Command "Read Memory with Password and CRC."
Command "Clear Memory with Password."
Command "Forced Conversion."
RMC
CM
FC
SM
Command "Start Mission with Password."
STP
Command "Stop Mission with Password."
TA
Target Address TA1, TA2.
TA–E/S
<Data to EOS>
<Data to EOP>
<PW/Dummy>
<32 Bytes>
<Data>
FFh
Target Address TA1, TA2 with E/S byte.
Transfer of as many data bytes as are needed to reach the scratchpad offset 1Fh.
Transfer of as many data bytes as are needed to reach the end of a memory page.
Transfer of 8 bytes that either represent a valid password or acceptable dummy data.
Transfer of 32 bytes.
Transfer of an undetermined amount of data.
Transmission of one FFh byte.
CRC-16
FF Loop
AA Loop
Transfer of an inverted CRC-16.
Indefinite loop where the master reads FF bytes.
Indefinite loop where the master reads AA bytes.
38 ______________________________________________________________________________________
High-Temperature Logger iButton with 8KB
Data-Log Memory
DS192E
Command-Specific 1-Wire Communication Protocol—Color Codes
Master-to-Slave Slave-to-Master
1-Wire Communication Examples
Write Scratchpad, Reaching the End of the Scratchpad (Cannot Fail)
RST PD Select WS TA <Data to EOS> CRC-16 FF Loop
Read Scratchpad (Cannot Fail)
RST PD Select RS TA-E/S <Data to EOS> CRC-16 FF Loop
Copy Scratchpad with Password (Success)
RST PD Select CPS TA-E/S <PW/Dummy> AA Loop
Copy Scratchpad with Password (Fail TA-E/S or Password)
RST PD Select CPS TA-E/S <PW/Dummy> FF Loop
Read Memory with Password and CRC (Success)
RST PD Select RMC TA <PW/Dummy> <Data to EOP> CRC-16
<32 Bytes>
CRC-16 FF Loop
Loop
Read Memory with Password and CRC (Fail Password or Address)
RST PD Select RMC TA <PW/Dummy> FF Loop
Clear Memory with Password
RST PD Select CM <PW/Dummy> FFh FF Loop
To verify success, read the General Status register at address 0215h. If MEMCLR is 1, the command was
executed successfully.
______________________________________________________________________________________ 39
High-Temperature Logger iButton with 8KB
Data-Log Memory
1-Wire Communication Examples (continued)
Forced Conversion
RST PD Select FC FFh FF Loop
To read the result and to verify success, read the addresses 020Ch to 020Fh (results) and the device samples
counter at address 0223h to 0225h. If the count has incremented, the command was executed successfully.
DS192E
Start Mission with Password
RST PD Select SM <PW/Dummy> FFh FF Loop
To verify success, read the General Status register at address 0215h. If MIP is 1 and MEMCLR is 0, the command
was executed successfully.
Stop Mission with Password
RST PD Select STP <PW/Dummy> FFh FF Loop
To verify success, read the General Status register at address 0215h. If MIP is 0, the command was executed
successfully.
Step 1: Clear the data of the previous mission.
Mission Example: Prepare
and Start a New Mission
Assumption: The previous mission has been ended by
Step 2: Write the setup data to register page 1.
Step 3: Start the new mission.
using the Stop Mission command. Passwords are not
enabled.
Step 1: Clear the data of the previous mission.
With only a single device connected to the bus master,
the communication of step 1 looks like this:
Starting a mission requires three steps:
MASTER MODE
DATA (LSB FIRST)
(Reset)
COMMENTS
Tx
Rx
Tx
Tx
Tx
Tx
Tx
Rx
Reset pulse
(Presence)
CCh
Presence pulse
Issue “Skip ROM” command
Issue “Clear Memory” command
Send dummy password
Send dummy byte
Reset pulse
96h
<8 FFh bytes>
FFh
(Reset)
(Presence)
Presence pulse
40 ______________________________________________________________________________________
High-Temperature Logger iButton with 8KB
Data-Log Memory
DS192E
Step 2: Write the setup data to register page 1.
• Alarm Controls (Response to Conditional Search)
During the setup, the device needs to learn the follow-
ing information:
• General Mission Parameters (e.g., Channels to Log
and Logging Format, Rollover, Start Mode)
• Time and Date
• Sample Rate
• Mission Start Delay
The following data sets up the DS1922E for a mission
that logs temperature using 8-bit format.
• Alarm Thresholds
ADDRESS
0200h
0201h
0202h
0203h
0204h
0205h
0206h
0207h
0208h
0209h
020Ah
020Bh
020Ch
020Dh
020Eh
020Fh
0210h
0211h
0212h
0213h
0214h
0215h
0216h
0217h
0218h
DATA
00h
30h
15h
01h
04h
08h
0Ah
00h
08h
F2h
00h
FFh
FFh
FFh
FFh
FFh
02h
FCh
01h
C1h
FFh
FFh
5Ah
00h
00h
EXAMPLE VALUES
FUNCTION
15:30:00 hours
Time
1st of April in 2008
Date
Every 10 minutes (EHSS = 0)
Sample rate
18°C low
135°C high
Temperature alarm thresholds
(Not applicable with DS1922E)
(Don’t care)
(Don’t care)
Clock through read-only registers
Enable high alarm
Disabled
Temperature alarm control
(Not applicable with DS1922E)
On (enabled), EHSS = 0 (low sample rate)
RTC oscillator control, sample rate selection
Normal start; no rollover; 8-bit temperature log General mission control
(Don’t care)
90 minutes
Clock through read-only registers
Mission start delay
______________________________________________________________________________________ 41
High-Temperature Logger iButton with 8KB
Data-Log Memory
With only a single device connected to the bus master,
the communication of step 2 looks like this:
MASTER MODE
DATA (LSB FIRST)
(Reset)
(Presence)
CCh
COMMENTS
Tx
Rx
Tx
Tx
Tx
Tx
Tx
Tx
Tx
Rx
Tx
Tx
Rx
Rx
Rx
Rx
Tx
Rx
Tx
Tx
Tx
Tx
Tx
Tx
Tx
Rx
Reset pulse
Presence pulse
Issue “Skip ROM” command
Issue “Write Scratchpad” command
TA1, beginning offset = 00h
TA2, address = 0200h
0Fh
DS192E
00h
02h
<25 Data Bytes>
<7 FFh Bytes>
(Reset)
(Presence)
CCh
Write 25 bytes of data to scratchpad
Write through the end of the scratchpad
Reset pulse
Presence pulse
Issue “Skip ROM” command
Issue “Read Scratchpad” command
Read TA1, beginning offset = 00h
Read TA2, address = 0200h
Read E/S, ending offset = 1Fh, flags = 0h
Read scratchpad data and verify
Reset pulse
AAh
00h
02h
1Fh
<32 Data Bytes>
(Reset)
(Presence)
CCh
Presence pulse
Issue “Skip ROM” command
Issue “Copy Scratchpad” command
TA1
99h
00h
(AUTHORIZATION CODE)
02h
TA2
E/S
1Fh
<8 FFh Bytes>
(Reset)
(Presence)
Send dummy password
Reset pulse
Presence pulse
Step 3: Start the new mission.
If step 3 was successful, the MIP bit in the General
Status register is 1, the MEMCLR bit is 0, and the mis-
sion start delay counts down.
With only a single device connected to the bus master,
the communication of step 3 looks like this:
MASTER MODE
DATA (LSB FIRST)
(Reset)
COMMENTS
Tx
Rx
Tx
Tx
Tx
Tx
Tx
Rx
Reset pulse
(Presence)
CCh
Presence pulse
Issue “Skip ROM” command
Issue “Start Mission” command
Send dummy password
Send dummy byte
Reset pulse
CCh
<8 FFh Bytes>
FFh
(Reset)
(Presence)
Presence pulse
42 ______________________________________________________________________________________
High-Temperature Logger iButton with 8KB
Data-Log Memory
DS192E
Software Correction Algorithm
for Temperature
Pin Configuration
F5 SIZE
The correction algorithm described in the DS1922L/
DS1922T data sheet does not apply to the DS1922E. If
attempted, the corrected result is generally less accu-
rate than the raw temperature data read from the
device. Therefore, with the DS1922E the memory pages
18 and 19 are available as additional user memory.
5.89mm
0.51mm
BRANDING
16.25mm
A1
41
®
000000FBC52B
®
1-Wire
®
Thermochron
17.35mm
IO
GND
Package Information
For the latest package outline information and land patterns, go to www.maxim-ic.com/packages.
PACKAGE TYPE
PACKAGE CODE
DOCUMENT NO.
21-0266
F5 iButton
IB#6CB
______________________________________________________________________________________ 43
High-Temperature Logger iButton with 8KB
Data-Log Memory
Revision History
REVISION REVISION
PAGES
CHANGED
DESCRIPTION
NUMBER
DATE
0
1
7/08
Initial release.
—
10/08
Added the Software Correction Algorithm for Temperature section.
43
Changed storage temperature range in Absolute Maximum Ratings and added a
recommended storage temperature note for maximum battery lifetime.
9
2
6/09
2
Maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim product. No circuit patent licenses are
implied. Maxim reserves the right to change the circuitry and specifications without notice at any time.
44 ____________________Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600
© 2009 Maxim Integrated Products
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