X1227V8 [INTERSIL]
2-Wire RTC Real TimeClock/Calendar/CPU Supervisor with EEPROM; 2线RTC实时时钟进度/日历/ CPU监控器， EEPROM
| 型号： | X1227V8 |
| 厂家： | 
Intersil |
| 描述： | 2-Wire RTC Real TimeClock/Calendar/CPU Supervisor with EEPROM |
| 文件： | 总28页 (文件大小：419K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
X1227
®
Data Sheet
September 15, 2005
FN8099.1
PRELIMINARY
™
APPLICATIONS
2-Wire RTC Real TimeClock/Calendar/
CPU Supervisor with EEPROM
• Utility Meters
• HVAC Equipment
• Audio / Video Components
• Set Top Box / Television
• Modems
• Network Routers, Hubs, Switches, Bridges
• Cellular Infrastructure Equipment
• Fixed Broadband Wireless Equipment
• Pagers / PDA
• POS Equipment
• Test Meters / Fixtures
• Office Automation (Copiers, Fax)
• Home Appliances
• Computer Products
FEATURES
• Real Time Clock/Calendar
— Tracks time in Hours, Minutes, and Seconds
— Day of the Week, Day, Month, and Year
• 2 Polled Alarms (Non-volatile)
— Settable on the Second, Minute, Hour, Day of the
Week, Day, or Month
— Repeat Mode (periodic interrupts)
• Oscillator Compensation on chip
— Internal feedback resistor and compensation
capacitors
— 64 position Digitally Controlled Trim Capacitor
— 6 digital frequency adjustment settings to ±30ppm
• CPU Supervisor Functions
— Power-on Reset, Low Voltage Sense
— Watchdog Timer (SW Selectable: 0.25s, 0.75s,
1.75s, off)
• Battery Switch or Super Cap Input
• 512 x 8 Bits of EEPROM
— 64-Byte Page Write Mode
— 8 modes of Block Lock™ Protection
— Single Byte Write Capability
• Other Industrial / Medical / Automotive
DESCRIPTION
The X1227 device is a Real Time Clock with
clock/calendar, two polled alarms with integrated 512x8
EEPROM, oscillator compensation, CPU Supervisor
(POR/LVS and WDT) and battery backup switch.
• High Reliability
— Data Retention: 100 years
The oscillator uses an external, low-cost 32.768kHz
crystal. All compensation and trim components are
integrated on the chip. This eliminates several external
discrete components and a trim capacitor, saving
board area and component cost.
— Endurance: 100,000 cycles per byte
• 2-Wire™ Interface interoperable with I2C*
— 400kHz data transfer rate
• Low Power CMOS
— 1.25µA Operating Current (Typical)
• Small Package Options
— 8-Lead SOIC and 8-Lead TSSOP
• Repetitive Alarms
• Temperature Compensation
• Pb-Free Plus Anneal Available (RoHS Compliant)
BLOCK DIAGRAM
OSC
Compensation
X1
Timer
Calendar
Logic
Battery
Switch
Circuitry
Time
Keeping
Registers
VCC
Frequency
Divider
1Hz
Oscillator
32.768kHz
VBACK
X2
(SRAM)
Status
Control/
Control
Decode
Logic
Compare
Serial
Interface
Decoder
Registers
SCL
SDA
Registers
Alarm
(EEPROM)
(SRAM)
Alarm Regs
(EEPROM)
8
4K
EEPROM
ARRAY
Watchdog
Timer
Low Voltage
Reset
RESET
CAUTION: These devices are sensitive to electrostatic discharge; follow proper IC Handling Procedures.
1
1-888-INTERSIL or 1-888-468-3774 | Intersil (and design) is a registered trademark of Intersil Americas Inc.
Copyright Intersil Americas Inc. 2005. All Rights Reserved
*I2C is a Trademark of Philips. All other trademarks mentioned are the property of their respective owners.
X1227
ORDERING INFORMATION
TEMPERATURE
RANGE (°C)
PART NUMBER
X1227S8-4.5A
X1227S8Z-4.5A (Note 1) X1227 Z AL
X1227S8I-4.5A X1227 AM
X1227S8IZ-4.5A (Note 1) X1227 Z AM
X1227V8-4.5A 1227AL
X1227V8Z-4.5A (Note 1) 1227AL Z
X1227V8I-4.5A 1227AM
X1227V8IZ-4.5A (Note 1) 1227AM Z
PART MARKING
VCC RANGE (V)
4.5 to 5.5
VTRIP
PACKAGE
8 Ld SOIC
X1227 AL
4.63V ± 112mV
0 to 70
0 to 70
8 Ld SOIC (Pb-free)
8 Ld SOIC
-40 to 85
-40 to 85
0 to 70
8 Ld SOIC (Pb-free)
8 Ld TSSOP
0 to 70
8 Ld TSSOP (Pb-free)
8 Ld TSSOP
-40 to 85
-40 to 85
0 to 70
8 Ld TSSOP (Pb-free)
8 Ld SOIC
X1227S8*
X1227
4.38V ± 112mV
2.85V ± 100mV
2.65V ± 100mV
X1227S8Z* (Note 1)
X1227S8I
X1227 Z
X1227 I
X1227 Z I
1227
0 to 70
8 Ld SOIC (Pb-free)
8 Ld SOIC
-40 to 85
-40 to 85
0 to 70
X1227S8IZ (Note 1)
X1227V8
8 Ld SOIC (Pb-free)
8 Ld TSSOP
X1227V8Z (Note 1)
X1227V8I
1227 Z
1227I
0 to 70
8 Ld TSSOP (Pb-free)
8 Ld TSSOP
-40 to 85
-40 to 85
0 to 70
X1227V8IZ (Note 1)
X1227S8-2.7A
1227I Z
X1227 AN
8 Ld TSSOP (Pb-free)
8 Ld SOIC
2.7 to 5.5
X1227S8Z-2.7A (Note 1) X1227 Z AN
X1227S8I-2.7A* X1227 AP
X1227S8IZ-2.7A* (Note 1) X1227 Z AP
X1227V8-2.7A 1227AN
X1227V8Z-2.7A (Note 1) 1227AN Z
X1227V8I-2.7A 1227AP
X1227V8IZ-2.7A (Note 1) 1227AP Z
0 to 70
8 Ld SOIC (Pb-free)
8 Ld SOIC
-40 to 85
-40 to 85
0 to 70
8 Ld SOIC (Pb-free)
8 Ld TSSOP
0 to 70
8 Ld TSSOP (Pb-free)
8 Ld TSSOP
-40 to 85
-40 to 85
0 to 70
8 Ld TSSOP (Pb-free)
8 Ld SOIC
X1227S8-2.7*
X1227 F
X1227 Z F
X1227 G
X1227 Z G
1227F
X1227S8Z-2.7 (Note 1)
X1227S8I-2.7*
0 to 70
8 Ld SOIC (Pb-free)
8 Ld SOIC
-40 to 85
-40 to 85
0 to 70
X1227S8IZ-2.7 (Note 1)
X1227V8-2.7
8 Ld SOIC (Pb-free)
8 Ld TSSOP
X1227V8Z-2.7 (Note 1)
X1227V8I-2.7
1227F Z
1227G
0 to 70
8 Ld TSSOP (Pb-free)
8 Ld TSSOP
-40 to 85
-40 to 85
X1227V8IZ-2.7 (Note 1)
1227G Z
8 Ld TSSOP (Pb-free)
*Add "T1" suffix for tape and reel.
NOTES:
1. Intersil Pb-free plus anneal products employ special Pb-free material sets; molding compounds/die attach materials and 100% matte tin plate
termination finish, which are RoHS compliant and compatible with both SnPb and Pb-free soldering operations. Intersil Pb-free products are
MSL classified at Pb-free peak reflow temperatures that meet or exceed the Pb-free requirements of IPC/JEDEC J STD-020.
2. For appropriate volume, any VTRIP value from 2.6 to 4.7V may be ordered via Intersil’s Customer Specification Program (CSPEC).
FN8099.1
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September 15, 2005
X1227
PIN DESCRIPTIONS
X1227
X1227
8-Pin TSSOP
8-Pin SOIC
V
SCL
SDA
BACK
1
2
8
7
6
5
1
2
V
V
X1
X2
8
7
6
5
CC
V
CC
BACK
V
SS
X1
X2
3
4
RESET
3
4
SCL
SDA
RESET
V
SS
NC = No internal connection
PIN ASSIGNMENTS
Pin Number
SOIC
TSSOP
Symbol
Brief Description
1
3
X1
X1. The X1 pin is the input of an inverting amplifier and should be connected to one
pin of a 32.768kHz quartz crystal.
2
3
4
5
X2
X2. The X2 pin is the output of an inverting amplifier and should be connected to
one pin of a 32.768kHz quartz crystal..
RESET
Reset Output – RESET. This is a reset signal output. This signal notifies a host
processor that the watchdog time period has expired or that the voltage has
dropped below a fixed V
threshold. It is an open drain active LOW output.
TRIP
4
5
6
7
VSS
VSS.
SDA
Serial Data (SDA). SDA is a bidirectional pin used to transfer data into and out of
the device. It has an open drain output and may be wire ORed with other open drain
or open collector outputs.
6
7
8
1
SCL
Serial Clock (SCL). The SCL input is used to clock all data into and out of the
device. The input buffer on this pin is always active (not gated).
VBACK
VBACK. This input provides a backup supply voltage to the device. VBACK supplies
power to the device in the event the VCC supply fails. This pin can be connected to
a battery, a Supercap or tied to ground if not used.
8
2
VCC
VCC.
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September 15, 2005
X1227
ABSOLUTE MAXIMUM RATINGS
Temperature Under Bias................... -65°C to +135°C
Storage Temperature ........................ -65°C to +150°C
Stresses above those listed under “Absolute Maximum
Ratings” may cause permanent damage to the device.
This is a stress rating only and the functional operation
of the device at these or any other conditions above
those indicated in the operational sections of this
specification is not implied. Exposure to absolute max-
imum rating conditions for extended periods may
affect device reliability.
Voltage on V , V
pin
CC BACK
(respect to ground)...............................-0.5V to 7.0V
Voltage on SCL, SDA, X1 and X2
pin (respect to ground) ............... -0.5V to 7.0V or 0.5V
above V or V
(whichever is higher)
CC
BACK
DC Output Current ..............................................5 mA
Lead Temperature (Soldering, 10 sec).............. 300°C
DC OPERATING CHARACTERISTICS (Temperature = -40°C to +85°C, unless otherwise stated.)
Symbol
VCC
Parameter
Conditions
Min
2.7
Typ
Max
5.5
Unit
V
Notes
Main Power Supply
Backup Power Supply
Switch to Backup Supply
Switch to Main Supply
VBACK
VCB
1.8
5.5
V
VBACK -0.2
VBACK
VBACK -0.1
VBACK +0.2
V
VBC
V
OPERATING CHARACTERISTICS
Symbol
Parameter
Conditions
VCC = 2.7V
VCC = 5.0V
VCC = 2.7V
VCC = 5.0V
VCC = 2.7V
VCC = 5.0V
VBACK = 1.8V
VBACK = 3.3V
Min
Typ
Max
400
800
2.5
3.0
10
Unit
µA
Notes
ICC1
Read Active Supply
Current
1, 5, 7, 14
µA
ICC2
Program Supply Current
(nonvolatile)
mA
mA
µA
2, 5, 7, 14
ICC3
Main Timekeeping
Current
3, 7, 8, 14, 15
20
µA
IBACK
Timekeeping Current –
(Low Voltage Sense
and Watchdog Timer
disabled
1.25
1.5
µA
3, 6, 9, 14, 15
“See Perfor-
mance Data”
µA
ILI
Input Leakage Current
Output Leakage Current
Input LOW Voltage
10
10
µA
µA
V
10
10
13
ILO
VIL
-0.5
VCC x 0.2 or
VBACK x 0.2
VIH
Input HIGH Voltage
VCC x 0.7 or
VBACK x 0.7
V
CC + 0.5 or
V
V
V
13
13
11
VBACK + 0.5
VHYS
VOL1
Schmitt Trigger Input
Hysteresis
VCC related level .05 x VCC or
.05 x VBACK
Output LOW Voltage for
SDA and RESET
VCC = 2.7V
VCC = 5.5V
0.4
0.4
Notes: (1) The device enters the Active state after any start, and remains active: for 9 clock cycles if the Device Select Bits in the Slave Address
Byte are incorrect or until 200nS after a stop ending a read or write operation.
(2) The device enters the Program state 200nS after a stop ending a write operation and continues for tWC
.
(3) The device goes into the Timekeeping state 200nS after any stop, except those that initiate a nonvolatile write cycle; tWC after a stop
that initiates a nonvolatile write cycle; or 9 clock cycles after any start that is not followed by the correct Device Select Bits in the Slave
Address Byte.
(4) For reference only and not tested.
(5) VIL = VCC x 0.1, VIH = VCC x 0.9, fSCL = 400KHz
(6) VCC = 0V
(7) VBACK = 0V
(8) VSDA = VSCL=VCC, Others = GND or VCC
FN8099.1
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September 15, 2005
X1227
(9) VSDA =VSCL=VBACK, Others = GND or VBACK
(10)VSDA = GND or VCC, VSCL = GND or VCC, VRESET = GND or VCC
(11)IOL = 3.0mA at 5.5V, 1.5mA at 2.7V
(12)
IOH = -1.0mA at 5.5V, -0.4mA at 2.7V
(13)Threshold voltages based on the higher of Vcc or Vback.
(14)Using recommended crystal and oscillator network applied to X1 and X2 (25°C).
(15)Typical values are for TA = 25°C
Capacitance T = 25°C, f = 1.0 MHz, V = 5V
A
CC
Symbol
Parameter
Max.
10
Units
pF
Test Conditions
VOUT = 0V
(1)
COUT
Output Capacitance (SDA, RESET)
Input Capacitance (SCL)
(1)
CIN
10
pF
VIN = 0V
Notes: (1) This parameter is not 100% tested.
(2) The input capacitance between x1 and x2 pins can be varied between 5pF and 19.75pF by using analog trimming registers
AC CHARACTERISTICS
AC Test Conditions
Input Pulse Levels
VCC x 0.1 to VCC x 0.9
Input Rise and Fall Times
10ns
Input and Output Timing
Levels
VCC x 0.5
Output Load
Standard Output Load
Figure 1. Standard Output Load for testing the device with V = 5.0V
CC
Equivalent AC Output Load Circuit for V = 5V
CC
5.0V
For VOL= 0.4V
1533Ω
and IOL = 3 mA
SDA
100pF
FN8099.1
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September 15, 2005
X1227
AC Specifications (T = -40°C to +85°C, VCC = +2.7V to +5.5V, unless otherwise specified.)
A
Symbol
Parameter
Min.
Max. Units
fSCL
tIN
SCL Clock Frequency
400
kHz
ns
µs
µs
µs
µs
µs
µs
ns
µs
µs
ns
ns
ns
pF
Pulse width Suppression Time at inputs
SCL LOW to SDA Data Out Valid
Time the bus must be free before a new transmission can start
Clock LOW Time
50(1)
tAA
0.1
0.9
tBUF
1.3
tLOW
tHIGH
tSU:STA
tHD:STA
tSU:DAT
tHD:DAT
tSU:STO
tDH
1.3
Clock HIGH Time
0.6
Start Condition Setup Time
Start Condition Hold Time
Data In Setup Time
0.6
0.6
100
Data In Hold Time
0
0.6
Stop Condition Setup Time
Data Output Hold Time
50
tR
SDA and SCL Rise Time
20 +.1Cb(2)
20 +.1Cb(2)
300
300
400
tF
SDA and SCL Fall Time
Cb
Capacitive load for each bus line
Notes: (1) This parameter is not 100% tested.
(2) Cb = total capacitance of one bus line in pF.
TIMING DIAGRAMS
Bus Timing
tF
tHIGH
tLOW
tR
SCL
tSU:DAT
tSU:STA
tHD:DAT
tSU:STO
tHD:STA
SDA IN
tAA tDH
tBUF
SDA OUT
FN8099.1
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September 15, 2005
X1227
Write Cycle Timing
SCL
8th Bit of Last Byte
ACK
SDA
tWC
Stop
Start
Condition
Condition
Power-up Timing
Symbol
(2)
Parameter
Min.
Typ.
Max.
Units
ms
(1)
tPUR
Time from Power-up to Read
Time from Power-up to Write
1
5
(1)
tPUW
ms
Notes: (1) Delays are measured from the time VCC is stable until the specified operation can be initiated. These parameters are periodically
sampled and not 100% tested.
(2) Typical values are for TA = 25°C and VCC = 5.0V
Nonvolatile Write Cycle Timing
(1)
Symbol
Parameter
Write Cycle Time
Min.
Typ.
Max.
Units
(1)
tWC
5
10
ms
Notes: (1) tWC is the time from a valid stop condition at the end of a write sequence to the end of the self-timed internal nonvolatile write cycle. It is
the minimum cycle time to be allowed for any nonvolatile write by the user, unless Acknowledge Polling is used.
WATCHDOG TIMER/LOW VOLTAGE RESET OPERATING CHARACTERISTICS
Watchdog/Low Voltage Reset Parameters
Symbols
Parameters
Min.
Typ.
Max.
Unit
VPTRIP
Programmed Reset Trip Voltage
X1227-4.5A
X1227
X1227-2.7A
X1227-2.7
V
4.5
4.25
2.7
4.68
4.38
2.93
2.68
4.75
4.5
3.0
2.55
2.7
tRPD
VCC Detect to RESET LOW
500
400
ns
tPURST
Power-up Reset Time-out Delay
100
200
ms
tF
tR
VCC Fall Time
VCC Rise Time
10
10
µs
µs
tWDO
Watchdog Timer Period:
WD1 = 0, WD0 = 0
WD1 = 0, WD0 = 1
WD1 = 1, WD0 = 0
1.7
725
225
1.75
750
250
1.8
775
275
s
ms
ms
tRST
Watchdog Reset Time-out Delay
225
250
275
ms
tRSP
2-Wire interface
Reset Valid VCC
1
µs
V
VRVALID
1.0
FN8099.1
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7
X1227
V
Programming Timing Diagram
TRIP
VCC
(VTRIP
)
VTRIP
tTSU
tTHD
VP = 15V
RESET
VCC
VCC
tVPH
0 1 2 3 4 5 6 7
tVPO
tVPS
0 1 2 3 4 5 6
7
0 1 2 3 4 5 6 7
0 1 2 3 4 5 6 7
SCL
SDA
tRP
AEh
00h
03h/01h
00h
V
Programming Parameters
TRIP
Parameter
tVPS
Description
Min.
1
Max.
Units
µs
VTRIP Program Enable Voltage Setup time
VTRIP Program Enable Voltage Hold time
VTRIP Setup time
tVPH
tTSU
tTHD
tVPO
1
µs
1
µs
VTRIP Hold (stable) time
10
0
ms
µs
VTRIP Program Enable Voltage Off time
(Between successive adjustments)
tRP
VTRIP Program Recovery Period
(Between successive adjustments)
10
ms
VP
VTRAN
Vtv
Programming Voltage
14
1.7
-25
16
5.0
+25
V
V
VTRIP Programmed Voltage Range
VTRIP Program variation after programming
(Programmed at 25°C)
mV
VTRIP programming parameters are not 100% Tested.
FN8099.1
September 15, 2005
8
X1227
DESCRIPTION (continued)
Serial Clock (SCL)
The SCL input is used to clock all data into and out of
the device. The input buffer on this pin is always active
(not gated).
The Real-Time Clock keeps track of time with
separate registers for Hours, Minutes, Seconds. The
Calendar has separate registers for Date, Month, Year
and Day-of-week. The calendar is correct through
2099, with automatic leap year correction.
Serial Data (SDA)
SDA is a bidirectional pin used to transfer data into and
out of the device. It has an open drain output and may
be wire ORed with other open drain or open collector
outputs. The input buffer is always active (not gated).
The powerful Dual Alarms can be set to any
Clock/Calendar value for a match. For instance, every
minute, every Tuesday, or 5:23 AM on March 21. The
alarms can be polled in the Status Register. There is a
repeat mode for the alarms allowing a periodic interrupt.
An open drain output requires the use of a pull-up
resistor. The output circuitry controls the fall time of
the output signal with the use of a slope controlled
pull-down. The circuit is designed for 400kHz 2-wire
interface speeds.
The X1227 device integrates CPU Supervisor func-
tions and a Battery Switch. There is a Power-On Reset
(RESET output) with typically 250 ms delay from
power-on. It will also assert RESET when Vcc goes
below the specified threshold. The V
threshold is
V
BACK
trip
user repro-grammable. There is a WatchDog Timer
(WDT) with 3 selectable time-out periods (0.25s,
0.75s, 1.75s) and a disabled setting. The watchdog
activates the RESET pin when it expires.
This input provides a backup supply voltage to the
device. V supplies power to the device in the
BACK
event the V supply fails. This pin can be connected
CC
to a battery, a Supercap or tied to ground if not used.
The device offers a backup power input pin. This
RESET Output – RESET
V
pin allows the device to be backed up by
BACK
This is a reset signal output. This signal notifies a host
processor that the watchdog time period has expired or
that the voltage has dropped below a fixed V
old. It is an open drain active LOW output. Recom-
mended value for the pullup resistor is 5kΩ. If unused, tie
to ground.
battery or SuperCap. The entire X1227 device is fully
operational from 2.7 to 5.5 volts and the
clock/calendar portion of the X1227 device remains
fully operational down to 1.8 volts (Standby Mode).
thresh-
TRIP
The X1227 device provides 4K bits of EEPROM with 8
modes of BlockLock™ control. The BlockLock allows a
safe, secure memory for critical user and configuration
data, while allowing a large user storage area.
X1, X2
The X1 and X2 pins are the input and output,
respectively, of an inverting amplifier. An external
32.768kHz quartz crystal is used with the X1227 to
supply a timebase for the real time clock. The
recommended crystal is a Citizen CFS206-32.768KDZF.
Internal compensation circuitry is included to form a
complete oscillator circuit. Care should be taken in the
placement of the crystal and the layout of the circuit.
Plenty of ground plane around the device and short
traces to X1 and X2 are highly recommended. See
Application section for more recommendations.
PIN DESCRIPTIONS
X1227
8-Pin SOIC
1
2
VCC
X1
X2
8
7
6
5
VBACK
SCL
RESET
VSS
3
4
SDA
X1227
8-Pin TSSOP
Figure 2. Recommended Crystal connection
VBACK
VCC
SCL
1
2
8
7
6
5
SDA
VSS
X1
X2
X1
X2
3
4
RESET
NC = No internal connection
FN8099.1
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September 15, 2005
X1227
POWER CONTROL OPERATION
the stop bit is written. The RTC continues to update
the time while an RTC register write is in progress and
the RTC continues to run during any nonvolatile write
sequences. A single byte may be written to the RTC
without affecting the other bytes.
The power control circuit accepts a V
and a V
BACK
CC
input. The power control circuit powers the device from
when V < V - 0.2V. It will switch back to
V
BACK
CC
BACK
power the device from V when V exceeds V
.
CC
CC
BACK
Figure 3. Power Control
Accuracy of the Real Time Clock
The accuracy of the Real Time Clock depends on the
frequency of the quartz crystal that is used as the time
base for the RTC. Since the resonant frequency of a
crystal is temperature dependent, the RTC perfor-
mance will also be dependent upon temperature. The
frequency deviation of the crystal is a fuction of the
turnover temperature of the crystal from the crystal’s
nominal frequency. For example, a >20ppm frequency
deviation translates into an accuracy of >1 minute per
month. These parameters are available from the
crystal manufacturer. Intersil’s RTC family provides
on-chip crystal compensation networks to adjust load-
capacitance to tune oscillator frequency from +116
ppm to -37 ppm when using a 12.5 pF load crystal. For
more detail information see the Application section.
VCC
Voltage
On
VBACK
In
Off
REAL TIME CLOCK OPERATION
The Real Time Clock (RTC) uses an external
32.768kHz quartz crystal to maintain an accurate inter-
nal representation of the second, minute, hour, day,
date, month, and year. The RTC has leap-year correc-
tion. The clock also corrects for months having fewer
than 31 days and has a bit that controls 24 hour or
AM/PM format. When the X1227 powers up after the
CLOCK/CONTROL REGISTERS (CCR)
loss of both V and V
, the clock will not operate
CC
BACK
The Control/Clock Registers are located in an area
separate from the EEPROM array and are only
accessible following a slave byte of “1101111x” and
reads or writes to addresses [0000h:003Fh]. The
clock/control memory map has memory addresses
from 0000h to 003Fh. The defined addresses are
described in the Table 1. Writing to and reading from
the undefined addresses are not recommended.
until at least one byte is written to the clock register.
Reading the Real Time Clock
The RTC is read by initiating a Read command and
specifying the address corresponding to the register of
the Real Time Clock. The RTC Registers can then be
read in a Sequential Read Mode. Since the clock runs
continuously and a read takes a finite amount of time,
there is the possibility that the clock could change during
the course of a read operation. In this device, the time is
latched by the read command (falling edge of the clock
on the ACK bit prior to RTC data output) into a separate
latch to avoid time changes during the read operation.
The clock continues to run. Alarms occurring during a
read are unaffected by the read operation.
CCR access
The contents of the CCR can be modified by perform-
ing a byte or a page write operation directly to any
address in the CCR. Prior to writing to the CCR
(except the status register), however, the WEL and
RWEL bits must be set using a two step process (See
section “Writing to the Clock/Control Registers.”)
Writing to the Real Time Clock
The CCR is divided into 5 sections. These are:
The time and date may be set by writing to the RTC
registers. To avoid changing the current time by an
uncompleted write operation, the current time value is
loaded into a separate buffer at the falling edge of the
clock on the ACK bit before the RTC data input bytes,
the clock continues to run. The new serial input data
replaces the values in the buffer. This new RTC value
is loaded back into the RTC Register by a stop bit at
the end of a valid write sequence. An invalid write
operation aborts the time update procedure and the
contents of the buffer are discarded. After a valid write
operation the RTC will reflect the newly loaded data
beginning with the next “one second” clock cycle after
1. Alarm 0 (8 bytes; non-volatile)
2. Alarm 1 (8 bytes; non-volatile)
3. Control (4 bytes; non-volatile)
4. Real Time Clock (8 bytes; volatile)
5. Status (1 byte; volatile)
Each register is read and written through buffers. The
non-volatile portion (or the counter portion of the RTC)
is updated only if RWEL is set and only after a valid
write operation and stop bit. A sequential read or page
write operation provides access to the contents of only
one section of the CCR per operation. Access to
another section requires a new operation. Continued
FN8099.1
10
September 15, 2005
X1227
reads or writes, once reaching the end of a section, will
wrap around to the start of the section. A read or write
can begin at any address in the CCR.
the CCR, the address remains at the previous address
+1 so the user can execute a current address read of
the CCR and continue reading the next Register.
It is not necessary to set the RWEL bit prior to writing
the status register. Section 5 supports a single byte
read or write only. Continued reads or writes from this
section terminates the operation.
ALARM REGISTERS
There are two alarm registers whose contents mimic the
contents of the RTC register, but add enable bits and
exclude the 24 hour time selection bit. The enable bits
specify which registers to use in the comparison between
the Alarm and Real Time Registers. For example:
The state of the CCR can be read by performing a ran-
dom read at any address in the CCR at any time. This
returns the contents of that register location. Additional
registers are read by performing a sequential read.
The read instruction latches all Clock registers into a
buffer, so an update of the clock does not change the
time being read. A sequential read of the CCR will not
result in the output of data from the memory array. At
the end of a read, the master supplies a stop condition
to end the operation and free the bus. After a read of
– Setting the Enable Month bit (EMOn*) bit in combi-
nation with other enable bits and a specific alarm
time, the user can establish an alarm that triggers at
the same time once a year.
– *n = 0 for Alarm 0: N = 1 for Alarm 1
Table 1. Clock/Control Memory Map
Bit
Reg
Name
Addr.
Type
Range
7
6
5
4
3
2
1
0 (optional)
003F
Status
SR
Y2K
DW
YR
MO
DT
HR
MN
SC
BAT
0
0
Y23
0
0
MIL
0
0
0
0
AL1
0
0
Y22
0
0
AL0
Y2K21
0
Y21
0
D21
H21
M21
S21
0
0
Y2K20
0
Y20
G20
D20
H20
M20
S20
0
0
Y2K13
0
Y13
G13
D13
H13
M13
S13
0
ATR3
Unused
WD0
A1Y2K13
0
RWEL
0
DY2
Y12
G12
D12
H12
M12
S12
DTR2
ATR2
WEL
0
RTCF
Y2K10
DY0
Y10
G10
D10
H10
M10
S10
01h
20h
00h
00h
00h
00h
00h
00h
00h
00h
00h
0037 RTC (SRAM)
19/20
0-6
0036
0035
0034
0033
0032
0031
0030
DY1
Y11
G11
D11
H11
M11
S11
DTR1
ATR1
0-99
1-12
1-31
0-23
0-59
0-59
0
M22
S22
0
0013
0012
0011
0010
000F
000E
000D
000C
000B
000A
0009
0008
0007
0006
0005
0004
0003
0002
0001
0000
Control
(EEPROM)
DTR
ATR
INT
DTR0
ATR0
0
ATR5
ATR4
BL
BP2
0
EDW1
BP1
0
BP0
A1Y2K21
0
WD1
A1Y2K20
0
0
0
DY2
0
0
DY1
0
18h
20h
00h
Alarm1
(EEPROM)
Y2K1
DWA1
YRA1
MOA1
DTA1
HRA1
MNA1
SCA1
Y2K0
DWA0
YRA0
MOA0
DTA0
HRA0
MNA0
SCA0
A1Y2K10
DY0
19/20
0-6
0
Unused - Default = RTC Year value (No EEPROM) - Future expansion
EMO1
EDT1
EHR1
EMN1
ESC1
0
0
0
0
A1G20
A1D20
A1H20
A1M20
A1S20
A0Y2K20
0
A1G13
A1D13
A1H13
A1M13
A1S13
A0Y2K13
0
A1G12
A1D12
A1H12
A1M12
A1S12
0
A1G11
A1D11
A1H11
A1M11
A1S11
0
A1G10
A1D10
A1H10
A1M10
A1S10
A0Y2K10
DY0
1-12
1-31
0-23
0-59
0-59
19/20
0-6
00h
00h
00h
00h
00h
20h
00h
A1D21
A1H21
A1M21
A1S21
A0Y2K21
0
0
A1M22
A1S22
0
Alarm0
(EEPROM)
EDW0
0
DY2
DY1
Unused - Default = RTC Year value (No EEPROM) - Future expansion
EMO0
EDT0
EHR0
EMN0
ESC0
0
0
0
0
A0G20
A0D20
A0H20
A0M20
A0S20
A0G13
A0D13
A0H13
A0M13
A0S13
A0G12
A0D12
A0H12
A0M12
A0S12
A0G11
A0D11
A0H11
A0M11
A0S11
A0G10
A0D10
A0H10
A0M10
A0S10
1-12
1-31
0-23
0-59
0-59
00h
00h
00h
00h
00h
A0D21
A0H21
A0M21
A0S21
A0M22
A0S22
FN8099.1
11
September 15, 2005
X1227
When there is a match, an alarm flag is set. The occur-
rence of an alarm can be determined by polling the
AL0 and AL1 bits or by enabling the IRQ output, using
it as hardware flag.
enable latches, read two power status and two alarm
bits. This register is separate from both the array and
the Clock/Control Registers (CCR).
Table 2. Status Register (SR)
The alarm enable bits are located in the MSB of the
particular register. When all enable bits are set to ‘0’,
there are no alarms.
Addr
003Fh BAT AL1 AL0
Default
7
6
5
4
3
2
1
0
0
0
0
0
RWEL WEL RTCF
– The user can set the X1227 to alarm every Wednes-
day at 8:00 AM by setting the EDWn*, the EHRn*
and EMNn* enable bits to ‘1’ and setting the DWAn*,
HRAn* and MNAn* Alarm registers to 8:00 AM
Wednesday.
0
0
0
0
0
1
BAT: Battery Supply—Volatile
This bit set to “1” indicates that the device is operating
from V , not V . It is a read-only bit and is set/reset
BACK
CC
– A daily alarm for 9:30PM results when the EHRn*
and EMNn* enable bits are set to ‘1’ and the HRAn*
and MNAn* registers are set to 9:30 PM.
by hardware (X1227 internally). Once the device begins
operating from V , the device sets this bit to “0”.
CC
AL1, AL0: Alarm bits—Volatile
*n = 0 for Alarm 0: N = 1 for Alarm 1
These bits announce if either alarm 0 or alarm 1 match
the real time clock. If there is a match, the respective
bit is set to ‘1’. The falling edge of the last data bit in a
SR Read operation resets the flags. Note: Only the AL
bits that are set when an SR read starts will be reset.
An alarm bit that is set by an alarm occurring during an
SR read operation will remain set after the read opera-
tion is complete.
REAL TIME CLOCK REGISTERS
Clock/Calendar Registers (SC, MN, HR, DT, MO, YR)
These registers depict BCD representations of the
time. As such, SC (Seconds) and MN (Minutes) range
from 00 to 59, HR (Hour) is 1 to 12 with an AM or PM
indicator (H21 bit) or 0 to 23 (with MIL = 1), DT (Date)
is 1 to 31, MO (Month) is 1 to 12, YR (Year) is 0 to 99.
RWEL: Register Write Enable Latch—Volatile
Date of the Week Register (DW)
This bit is a volatile latch that powers up in the LOW
(disabled) state. The RWEL bit must be set to “1” prior
to any writes to the Clock/Control Registers. Writes to
RWEL bit do not cause a nonvolatile write cycle, so the
device is ready for the next operation immediately after
the stop condition. A write to the CCR requires both the
RWEL and WEL bits to be set in a specific sequence.
This register provides a Day of the Week status and
uses three bits DY2 to DY0 to represent the seven
days of the week. The counter advances in the cycle
0-1-2-3-4-5-6-0-1-2-… The assignment of a numerical
value to a specific day of the week is arbitrary and may
be decided by the system software designer. The
default value is defined as ‘0’.
WEL: Write Enable Latch—Volatile
24 Hour Time
The WEL bit controls the access to the CCR and mem-
ory array during a write operation. This bit is a volatile
latch that powers up in the LOW (disabled) state. While
the WEL bit is LOW, writes to the CCR or any array
address will be ignored (no acknowledge will be issued
after the Data Byte). The WEL bit is set by writing a “1”
to the WEL bit and zeroes to the other bits of the Status
Register. Once set, WEL remains set until either reset
to 0 (by writing a “0” to the WEL bit and zeroes to the
other bits of the Status Register) or until the part powers
up again. Writes to WEL bit do not cause a nonvolatile
write cycle, so the device is ready for the next operation
immediately after the stop condition.
If the MIL bit of the HR register is 1, the RTC uses a
24-hour format. If the MIL bit is 0, the RTC uses a 12-
hour format and H21 bit functions as an AM/PM indi-
cator with a ‘1’ representing PM. The clock defaults to
standard time with H21 = 0.
Leap Years
Leap years add the day February 29 and are defined
as those years that are divisible by 4. Years divisible
by 100 are not leap years, unless they are also divisi-
ble by 400. This means that the year 2000 is a leap
year, the year 2100 is not. The X1227 does not correct
for the leap year in the year 2100.
RTCF: Real Time Clock Fail Bit—Volatile
STATUS REGISTER (SR)
This bit is set to a ‘1’ after a total power failure. This is
a read only bit that is set by hardware (X1227 inter-
nally) when the device powers up after having lost all
power to the device. The bit is set regardless of
The Status Register is located in the CCR Memory
Map at address 003Fh. This is a volatile register only
and is used to control the WEL and RWEL write
FN8099.1
12
September 15, 2005
X1227
whether V or V
is applied first. The loss of only
BACK
Watchdog Timer Control Bits—WD1, WD0
CC
one of the supplies does not result in setting the RTCF
bit. The first valid write to the RTC after a complete
power failure (writing one byte is sufficient) resets the
RTCF bit to ‘0’.
The bits WD1 and WD0 control the period of the
Watchdog Timer. See Table 4 for options.
Table 4. Watchdog Timer Time-Out Options
Watchdog Time-Out Period
WD1 WD0
Unused Bits:
This device does not use bits 3 or 4 in the SR, but must
have a zero in these bit positions. The Data Byte output
during a SR read will contain zeros in these bit locations.
0
0
1
1
0
1
0
1
1.75 seconds
750 milliseconds
250 milliseconds
Disabled (default)
CONTROL REGISTERS
The Control Bits and Registers, described under this
section, are nonvolatile.
ON-CHIP OSCILLATOR COMPENSATION
Digital Trimming Register (DTR) — DTR2, DTR1
and DTR0 (Non-Volatile)
Block Protect Bits—BP2, BP1, BP0
The Block Protect Bits, BP2, BP1 and BP0, determine
which blocks of the array are write protected. A write to a
protected block of memory is ignored. The block protect
bits will prevent write operations to one of eight segments
of the array. The partitions are described in Table 3 .
The digital trimming Bits DTR2, DTR1 and DTR0
adjust the number of counts per second and average
the ppm error to achieve better accuracy.
DTR2 is a sign bit. DTR2=0 means frequency
compensation is > 0. DTR2=1 means frequency
compensation is < 0.
Table 3. Block Protect Bits
Protected Addresses
DTR1 and DTR0 are scale bits. DTR1 gives 10 ppm
adjustment and DTR0 gives 20 ppm adjustment.
X1227
Array Lock
None
0
0
0
0
1
1
1
1
0
0
1
1
0
0
1
1
0
1
0
1
0
1
0
1
None (Default)
180h - 1FFh
A range from -30ppm to +30ppm can be represented
by using three bits above.
Upper 1/4
100h - 1FFh
000h - 1FFh
000h - 03Fh
000h - 07Fh
000h - 0FFh
000h - 1FFh
Upper 1/2
Full Array
First Page
First 2 pgs
First 4 pgs
First 8 pgs
Table 5. Digital Trimming Registers
DTR Register
Estimated frequency
DTR2
DTR1
DTR0
PPM
0 (Default)
+10
0
0
0
0
1
1
1
1
0
1
0
1
0
1
0
1
0
0
1
1
0
0
1
1
+20
+30
0
-10
-20
-30
FN8099.1
September 15, 2005
13
X1227
Analog Trimming Register (ATR) (Non-volatile)
– Write one to 8 bytes to the Clock/Control Registers
with the desired clock, alarm, or control data. This
sequence starts with a start bit, requires a slave byte
of “11011110” and an address within the CCR and is
terminated by a stop bit. A write to the CCR changes
EEPROM values so these initiate a nonvolatile write
cycle and will take up to 10ms to complete. Writes to
undefined areas have no effect. The RWEL bit is
reset by the completion of a nonvolatile write cycle,
so the sequence must be repeated to again initiate
another change to the CCR contents. If the
Six analog trimming Bits from ATR5 to ATR0 are pro-
vided to adjust the on-chip loading capacitance range.
The on-chip load capacitance ranges from 3.25pF to
18.75pF. Each bit has a different weight for capacitance
adjustment. Using a Citizen CFS-206 crystal with differ-
ent ATR bit combinations provides an estimated ppm
range from +116ppm to -37ppm to the nominal fre-
quency compensation. The combination of digital and
analog trimming can give up to +146ppm adjustment.
The on-chip capacitance can be calculated as follows:
sequence is not completed for any reason (by send-
ing an incorrect number of bits or sending a start
instead of a stop, for example) the RWEL bit is not
reset and the device remains in an active mode.
C
= [(ATR value, decimal) x 0.25pF] + 11.0pF
ATR
Note that the ATR values are in two’s complement,
with ATR(000000) = 11.0pF, so the entire range runs
from 3.25pF to 18.75pF in 0.25pF steps.
– Writing all zeros to the status register resets both the
WEL and RWEL bits.
The values calculated above are typical, and total load
capacitance seen by the crystal will include approxi-
mately 2pF of package and board capacitance in addi-
tion to the ATR value.
– A read operation occurring between any of the
previous operations will not interrupt the register
write operation.
See Application section and Intersil’s Application Note
AN154 for more information.
WRITING TO THE CLOCK/CONTROL REGISTERS
Changing any of the nonvolatile bits of the clock/con-
trol register requires the following steps:
– Write a 02h to the Status Register to set the Write
Enable Latch (WEL). This is a volatile operation,
so there is no delay after the write. (Operation
preceeded by a start and ended with a stop).
– Write a 06h to the Status Register to set both the
Register Write Enable Latch (RWEL) and the WEL
bit. This is also a volatile cycle. The zeros in the data
byte are required. (Operation preceeded by a start
and ended with a stop).
FN8099.1
14
September 15, 2005
X1227
POWER-ON RESET
Watchdog Timer Restart
The Watchdog Timer is started by a falling edge of
SDA when the SCL line is high and followed by a stop
bit. The start signal restarts the watchdog timer
counter, resetting the period of the counter back to the
maximum. If another start fails to be detected prior to
the watchdog timer expiration, then the RESET pin
becomes active. In the event that the start signal
occurs during a reset time out period, the start will
have no effect. When using a single START to refresh
watchdog timer, a STOP bit should be followed to
reset the device back to stand-by mode.
Application of power to the X1227 activates a Power-
on Reset Circuit that pulls the RESET pin active. This
signal provides several benefits.
– It prevents the system microprocessor from starting
to operate with insufficient voltage.
– It prevents the processor from operating prior to sta-
bilization of the oscillator.
– It allows time for an FPGA to download its configura-
tion prior to initialization of the circuit.
– It prevents communication to the EEPROM, greatly
reducing the likelihood of data corruption on power-up.
LOW VOLTAGE RESET OPERATION
When V
exceeds the device V
threshold value
CC
TRIP
When a power failure occurs, and the voltage to the
for typically 250ms the circuit releases RESET, allow-
ing the system to begin operation. Recommended
slew rate is between 0.2V/ms and 50V/ms.
part drops below a fixed v
voltage, a reset pulse is
TRIP
issued to the host microcontroller. The circuitry moni-
tors the V line with a voltage comparator which
CC
senses a preset threshold voltage. Power-up and
power-down waveforms are shown in Figure 5. The
Low Voltage Reset circuit is to be designed so the
RESET signal is valid down to 1.0V.
WATCHDOG TIMER OPERATION
The watchdog timer is selectable. By writing a value to
WD1 and WD0, the watchdog timer can be set to 3 dif-
ferent time out periods or off. When the Watchdog
timer is set to off, the watchdog circuit is configured for
low power operation.
When the low voltage reset signal is active, the operation
of any in progress nonvolatile write cycle is unaffected,
allowing a nonvolatile write to continue as long as possi-
ble (down to the power-on reset voltage). The low volt-
age reset signal, when active, terminates in progress
communications to the device and prevents new com-
mands, to reduce the likelihood of data corruption.
Figure 4. Watchdog Restart/Time Out
tRSP
tRSP>tWDO
tRST
tRSP>tWDO
tRST
tRSP<tWDO
SCL
SDA
RESET
Stop
Start
Start
Note: All inputs are ignored during the active reset period (tRST).
FN8099.1
15
September 15, 2005
X1227
Figure 5. Power-on Reset and Low Voltage Reset
V
TRIP
V
CC
t
t
PURST
PURST
t
RPD
t
F
t
R
RESET
V
RVALID
V
THRESHOLD RESET PROCEDURE
Setting the V
Voltage
CC
TRIP
[OPTIONAL]
It is necessary to reset the trip point before setting the
new value.
The X1227 is shipped with a standard V
threshold
CC
(V
) voltage. This value will not change over normal
TRIP
To set the new V
voltage, apply the desired
TRIP
operating and storage conditions. However, in applica-
tions where the standard V is not exactly right, or if
higher precision is needed in the V
X1227 threshold may be adjusted. The procedure is
described below, and uses the application of a nonvol-
atile write control signal.
V
threshold voltage to the V
pin and tie the
TRIP
CC
TRIP
RESET pin to the programming voltage V . Then
write data 00h to address 01h. The stop bit following
a valid write operation initiates the V
ming sequence. Bring RESET to V to complete the
operation. Note: this operation may take up to 10 mil-
liseconds to complete and also writes 00h to address
01h of the EEPROM array.
P
value, the
TRIP
program-
TRIP
CC
Figure 6. Set V
Level Sequence (V = desired V
value)
TRIP
CC
TRIP
VP = 15V
RESET
VCC
VCC
0
1
2
3
4
5 6 7
0
1
2
3
4
5
6
7
0
1
2
3
4
5
6
7
0
1
2
3
4
5 6 7
SCL
SDA
AEh
00h
01h
00h
Note: BP0, BP1, BP2 must be disabled.
Resetting the V
Voltage
For best accuracy in setting V
, it is advised that
TRIP
TRIP
the following sequence be used.
This procedure is used to set the V
to a “native”
TRIP
voltage level. For example, if the current V
is 4.4V
TRIP
1.Program V as above.
TRIP
and the new V
must be 4.0V, then the V
must
TRIP
TRIP
2.Measure resulting V
by measuring the V
CC
TRIP
be reset. When V
is reset, the new V
is some-
TRIP
TRIP
value where a RESET occurs. Calculate Delta =
(Desired - Measured) V value.
thing less than 1.7V. This procedure must be used to
set the voltage to a lower value.
TRIP
3.Perform a V
to set the voltage of the RESET pin:
program using the following formula
TRIP
To reset the new V
voltage, apply more than 3.0V
TRIP
to the V
pin and tie the RESET pin to the
CC
V
= (Desired Value – Delta) + 0.025V
RESET
programming voltage V . Then write 00h to address
P
03h. The stop bit of a valid write operation initiates the
V
programming sequence. Bring RESET to V to
TRIP
CC
complete the operation. Note: this operation takes up
to 10 milliseconds to complete and also writes 00h to
address 03h of the EEPROM array.
FN8099.1
September 15, 2005
16
X1227
Figure 7. Reset V
Level Sequence
TRIP
VP = 15V
RESET
VCC
VCC
0
1 2 3 4 5 6 7
0
1
2
3
4
5
6
7
0
1
2
3
4
5
6
7
0
1
2
3
4
5 6 7
SCL
SDA
AEh
00h
03h
00h
Note: BP0, BP1, BP2 must be disabled.
SERIAL COMMUNICATION
Interface Conventions
Acknowledge
Acknowledge is a software convention used to indi-
cate successful data transfer. The transmitting device,
either master or slave, will release the bus after trans-
mitting eight bits. During the ninth clock cycle, the
receiver will pull the SDA line LOW to acknowledge
that it received the eight bits of data. Refer to Figure 10.
The device supports a bidirectional bus oriented proto-
col. The protocol defines any device that sends data
onto the bus as a transmitter, and the receiving device
as the receiver. The device controlling the transfer is
called the master and the device being controlled is
called the slave. The master always initiates data
transfers, and provides the clock for both transmit and
receive operations. Therefore, the devices in this fam-
ily operate as slaves in all applications.
The device will respond with an acknowledge after
recognition of a start condition and if the correct
Device Identifier and Select bits are contained in the
Slave Address Byte. If a write operation is selected,
the device will respond with an acknowledge after the
receipt of each subsequent eight bit word. The device
will acknowledge all incoming data and address bytes,
except for:
Clock and Data
Data states on the SDA line can change only during
SCL LOW. SDA state changes during SCL HIGH are
reserved for indicating start and stop conditions. See
Figure 8.
– The Slave Address Byte when the Device Identifier
and/or Select bits are incorrect
– All Data Bytes of a write when the WEL in the Write
Protect Register is LOW
Start Condition
All commands are preceded by the start condition,
which is a HIGH to LOW transition of SDA when SCL
is HIGH. The device continuously monitors the SDA
and SCL lines for the start condition and will not
respond to any command until this condition has been
met. See Figure 9.
– The 2nd Data Byte of a Status Register Write Oper-
ation (only 1 data byte is allowed)
In the read mode, the device will transmit eight bits of
data, release the SDA line, then monitor the line for an
acknowledge. If an acknowledge is detected and no
stop condition is generated by the master, the device
will continue to transmit data. The device will terminate
further data transmissions if an acknowledge is not
detected. The master must then issue a stop condition
to return the device to Standby mode and place the
device into a known state.
Stop Condition
All communications must be terminated by a stop
condition, which is a LOW to HIGH transition of SDA
when SCL is HIGH. The stop condition is also used to
place the device into the Standby power mode after a
read sequence. A stop condition can only be issued
after the transmitting device has released the bus. See
Figure 9.
FN8099.1
17
September 15, 2005
X1227
Figure 8. Valid Data Changes on the SDA Bus
SCL
SDA
Data Stable
Data Change
Data Stable
Figure 9. Valid Start and Stop Conditions
SCL
SDA
Start
Stop
Figure 10. Acknowledge Response From Receiver
SCL from
Master
1
8
9
Data Output
from Transmitter
Data Output
from Receiver
Start
Acknowledge
DEVICE ADDRESSING
Following the Slave Byte is a two byte word address.
The word address is either supplied by the master
device or obtained from an internal counter. On power-
up the internal address counter is set to address 0h,
so a current address read of the EEPROM array starts
at address 0. When required, as part of a random
read, the master must supply the 2 Word Address
Bytes as shown in Figure 11.
Following a start condition, the master must output a
Slave Address Byte. The first four bits of the Slave
Address Byte specify access to either the EEPROM
array or to the CCR. Slave bits ‘1010’ access the
EEPROM array. Slave bits ‘1101’ access the CCR.
When shipped from the factory, EEPROM array is
UNDEFINED, and should be programmed by the cus-
tomer to a known state.
In a random read operation, the slave byte in the
“dummy write” portion must match the slave byte in
the “read” section. That is if the random read is from
the array the slave byte must be 1010111x in both
instances. Similarly, for a random read of the
Clock/Control Registers, the slave byte must be
1101111x in both places.
Bit 3 through Bit 1 of the slave byte specify the device
select bits. These are set to ‘111’.
The last bit of the Slave Address Byte defines the
operation to be performed. When this R/W bit is a one,
then a read operation is selected. A zero selects a
write operation. Refer to Figure 11.
After loading the entire Slave Address Byte from the
SDA bus, the X1227 compares the device identifier
and device select bits with ‘1010111’ or ‘1101111’.
Upon a correct compare, the device outputs an
acknowledge on the SDA line.
FN8099.1
18
September 15, 2005
X1227
Figure 11. Slave Address, Word Address, and Data Bytes (64 Byte pages)
Device Identifier
Slave Address Byte
Array
CCR
1
1
0
1
1
0
0
1
1
1
1
0
R/W
A8
Byte 0
Word Address 1
Byte 1
0
0
0
0
0
0
Word Address 0
Byte 2
A7
D7
A6
D6
A5
D5
A4
D4
A3
D3
A2
D2
A1
D1
A0
D0
Data Byte
Byte 3
Write Operations
Byte Write
the 8 data bits, the X1227 again responds with an
acknowledge. The master then terminates the transfer
by generating a stop condition. The X1227 then
begins an internal write cycle of the data to the nonvol-
atile memory. During the internal write cycle, the
device inputs are disabled, so the device will not
respond to any requests from the master. The SDA out-
put is at high impedance. See Figure 12.
For a write operation, the device requires the Slave
Address Byte and the Word Address Bytes. This gives
the master access to any one of the words in the array
or CCR. (Note: Prior to writing to the CCR, the master
must write a 02h, then 06h to the status register in two
preceding operations to enable the write operation.
See “Writing to the Clock/Control Registers.” Upon
receipt of each address byte, the X1227 responds with
an acknowledge. After receiving both address bytes
the X1227 awaits the eight bits of data. After receiving
A write to a protected block of memory is ignored, but
will still receive an acknowledge. At the end of the
write command, the X1227 will not initiate an internal
write cycle, and will continue to ACK commands.
Figure 12. Byte Write Sequence
S
t
a
r
Signals from
the Master
S
t
Slave
Address
Word
Address 1
Word
Address 0
o
t
Data
p
SDA Bus
1
1 1 1 0 0 0 0 0 0 0 0
A
C
K
A
C
K
A
C
K
A
C
K
Signals From
The Slave
Figure 13. Writing 30 bytes to a 64-byte memory page starting at address 40.
7 Bytes
23 Bytes
Address Pointer
Ends Here
Addr = 7
Address
Address
= 6
Address
40
63
FN8099.1
19
September 15, 2005
X1227
Page Write
bytes are written to columns 0 through 6. Afterwards,
the address counter would point to location 7 on the
page that was just written. If the master supplies more
than the maximum bytes in a page, then the previously
loaded data is over written by the new data, one byte at
a time. Refer to Figure 13.
The X1227 has a page write operation. It is initiated in
the same manner as the byte write operation; but
instead of terminating the write cycle after the first data
byte is transferred, the master can transmit up to 63
more bytes to the memory array and up to 7 more
bytes to the clock/control registers. (Note: Prior to writ-
ing to the CCR, the master must write a 02h, then 06h
to the status register in two preceding operations to
enable the write operation. See “Writing to the
Clock/Control Registers.”
The master terminates the Data Byte loading by issu-
ing a stop condition, which causes the X1227 to begin
the nonvolatile write cycle. As with the byte write oper-
ation, all inputs are disabled until completion of the
internal write cycle. Refer to Figure 14 for the address,
acknowledge, and data transfer sequence.
After the receipt of each byte, the X1227 responds with
an acknowledge, and the address is internally incre-
mented by one. When the counter reaches the end of
the page, it “rolls over” and goes back to the first
address on the same page. This means that the master
can write 64 bytes to a memory array page or 8 bytes to
a CCR section starting at any location on that page. For
example, if the master begins writing at location 40 of
the memory and loads 30 bytes, then the first 23 bytes
are written to addresses 45 through 63, and the last 7
Stops and Write Modes
Stop conditions that terminate write operations must be
sent by the master after sending at least 1 full data byte
and it’s associated ACK signal. If a stop is issued in the
middle of a data byte, or before 1 full data byte + ACK is
sent, then the X1227 resets itself without performing the
write. The contents of the array are not affected.
Figure 14. Page Write Sequence
1 ð n ð 64 for EEPROM array
1 ð n ð 8 for CCR
S
t
a
r
Signals from
the Master
S
t
o
p
Word
Address 1
Slave
Address
Word
Address 0
Data
(1)
Data
(n)
t
SDA Bus
1
1 1 1 0
0 0 0 0 0 0 0
A
C
K
A
C
K
A
C
K
A
C
K
Signals from
the Slave
FN8099.1
September 15, 2005
20
X1227
Acknowledge Polling
Figure 16. Acknowledge Polling Sequence
Disabling of the inputs during nonvolatile write cycles
can be used to take advantage of the typical 5mS write
cycle time. Once the stop condition is issued to indi-
cate the end of the master’s byte load operation, the
X1227 initiates the internal nonvolatile write cycle.
Acknowledge polling can begin immediately. To do
this, the master issues a start condition followed by the
Memory Array Slave Address Byte for a write or read
operation (AEh or AFh). If the X1227 is still busy with
the nonvolatile write cycle then no ACK will be
returned. When the X1227 has completed the write
operation, an ACK is returned and the host can pro-
ceed with the read or write operation. Refer to the flow
chart in Figure 16. Note: Do not use the CCR slave
byte (DEh or DFh) for acknowledge polling.
Byte load completed
by issuing STOP.
Enter ACK Polling
Issue START
Issue Memory Array Slave
Issue STOP
Address Byte AFh (Read)
or AEh (Write)
NO
ACK
returned?
YES
Read Operations
NO
nonvolatile write
Cycle complete. Continue
command sequence?
There are three basic read operations: Current
Address Read, Random Read, and Sequential Read.
Issue STOP
Current Address Read
YES
Internally the X1227 contains an address counter that
maintains the address of the last word read incre-
mented by one. Therefore, if the last read was to
address n, the next read operation would access data
from address n+1. On power-up, the sixteen bit
address is initialized to 0h. In this way, a current
address read immediately after the power-on reset
can download the entire contents of memory starting
at the first location.Upon receipt of the Slave Address
Byte with the R/W bit set to one, the X1227 issues an
acknowledge, then transmits eight data bits. The mas-
ter terminates the read operation by not responding
with an acknowledge during the ninth clock and issu-
ing a stop condition. Refer to Figure 15 for the
address, acknowledge, and data transfer sequence.
Continue normal
Read or Write
command
sequence
PROCEED
It should be noted that the ninth clock cycle of the read
operation is not a “don’t care.” To terminate a read
operation, the master must either issue a stop condi-
tion during the ninth cycle or hold SDA HIGH during
the ninth clock cycle and then issue a stop condition.
Figure 15. Current Address Read Sequence
S
t
S
t
o
p
Signals from
a
Slave
Address
the Master
r
t
SDA Bus
1
1 1 1 1
A
C
K
Signals from
the Slave
Data
FN8099.1
21
September 15, 2005
X1227
Random Read
read from the newly loaded address. This operation
could be useful if the master knows the next address it
needs to read, but is not ready for the data.
Random read operations allows the master to access
any location in the X1227. Prior to issuing the Slave
Address Byte with the R/W bit set to zero, the master
must first perform a “dummy” write operation.
Sequential Read
Sequential reads can be initiated as either a current
address read or random address read. The first data
byte is transmitted as with the other modes; however,
the master now responds with an acknowledge, indi-
cating it requires additional data. The device continues
to output data for each acknowledge received. The
master terminates the read operation by not responding
with an acknowledge and then issuing a stop condition.
The master issues the start condition and the slave
address byte, receives an acknowledge, then issues
the word address bytes. After acknowledging receipt
of each word address byte, the master immediately
issues another start condition and the slave address
byte with the R/W bit set to one. This is followed by an
acknowledge from the device and then by the eight bit
data word. The master terminates the read operation
by not responding with an acknowledge and then issu-
ing a stop condition. Refer to Figure 17 for the
address, acknowledge, and data transfer sequence.
The data output is sequential, with the data from
address n followed by the data from address n + 1.
The address counter for read operations increments
through all page and column addresses, allowing the
entire memory contents to be serially read during one
operation. At the end of the address space the counter
“rolls over” to the start of the address space and the
X1227 continues to output data for each acknowledge
received. Refer to Figure 18 for the acknowledge and
data transfer sequence.
In a similar operation called “Set Current Address,” the
device sets the address if a stop is issued instead of
the second start shown in Figure 17. The X1227 then
goes into standby mode after the stop and all bus
activity will be ignored until a start is detected. This
operation loads the new address into the address
counter. The next Current Address Read operation will
Figure 17. Random Address Read Sequence
S
t
S
S
t
o
p
t
a
r
Signals from
the Master
Slave
Address
Word
Address 0
Slave
Address
a
r
Word
Address 1
t
t
SDA Bus
1
1 1 1 1
1
1 1 1 0
0 0 0 0 0 0 0
A
C
K
A
C
K
A
C
K
A
C
K
Signals from
the Slave
Data
Figure 18. Sequential Read Sequence
S
t
o
p
Slave
Address
A
C
K
A
C
K
A
C
K
Signals from
the Master
SDA Bus
1
A
C
K
Signals from
the Slave
Data
(2)
Data
(n-1)
Data
(1)
Data
(n)
(n is any integer greater than 1)
FN8099.1
September 15, 2005
22
X1227
APPLICATION SECTION
the temperature extremes of -40 and +85 deg C. It is
possible to address this variable drift by adjusting the
load capacitance of the crystal, which will result in pre-
dictable change to the crystal frequency. The Intersil
RTC family allows this adjustment over temperature
since the devices include on-chip load capacitor trim-
ming. This control is handled by the Analog Trimming
Register, or ATR, which has 6 bits of control. The load
capacitance range covered by the ATR circuit is
approximately 3.25pF to 18.75pF, in 0.25pf incre-
ments. Note that actual capacitance would also
include about 2pF of package related capacitance. In-
circuit tests with commercially available crystals dem-
onstrate that this range of capacitance allows fre-
quency control from +116ppm to -37ppm, using a
12.5pF load crystal.
CRYSTAL OSCILLATOR AND TEMPERATURE
COMPENSATION
Intersil has now integrated the oscillator compensation
circuity on-chip, to eliminate the need for external
components and adjust for crystal drift over tempera-
ture and enable very high accuracy time keeping
(<5ppm drift.
The Intersil RTC family uses an oscillator circuit with
on-chip crystal compensation network, including
adjustable load-capacitance. The only external com-
ponent required is the crystal. The compensation net-
work is optimized for operation with certain crystal
parameters which are common in many of the surface
mount or tuning-fork crystals available today. Table 6
summarizes these parameters.
In addition to the analog compensation afforded by the
adjustable load capacitance, a digital compensation
feature is available for the Intersil RTC family. There
are three bits known as the Digital Trimming Register
or DTR, and they operate by adding or skipping pulses
in the clock signal. The range provided is ±30ppm in
increments of 10ppm. The default setting is 0ppm. The
DTR control can be used for coarse adjustments of
frequency drift over temperature or for crystal initial
accuracy correction.
Table 7 contains some crystal manufacturers and part
numbers that meet the requirements for the Intersil
RTC products.
The turnover temperature in Table 6 describes the
temperature where the apex of the of the drift vs. tem-
perature curve occurs. This curve is parabolic with the
drift increasing as (T-T0) . For an Epson MC-405
device, for example, the turnover temperature is typi-
cally 25 deg C, and a peak drift of >110ppm occurs at
2
Table 6. Crystal Parameters Required for Intersil RTC’s
Parameter
Min
Typ
Max
Units
kHz
ppm
°C
Notes
Frequency
32.768
Freq. Tolerance
±100
30
Down to 20ppm if desired
Turnover Temperature
20
25
Typically the value used for most
crystals
Operating Temperature Range
Parallel Load Capacitance
Equivalent Series Resistance
-40
85
50
°C
pF
kΩ
12.5
For best oscillator performance
Table 7. Crystal Manufacturers
Manufacturer
Citizen
Part Number
CM201, CM202, CM200S
MC-405, MC-406
RSM-200S-A or B
32S12A or B
Temp Range
-40 to +85°C
-40 to +85°C
-40 to +85°C
-40 to +85°C
-10 to +60°C
-10 to +60°C
-40 to +85°C
+25°C Freq Toler.
±20ppm
Epson
Raltron
SaRonix
Ecliptek
ECS
±20ppm
±20ppm
±20ppm
ECPSM29T-32.768K
ECX-306/ECX-306I
FSM-327
±20ppm
±20ppm
Fox
±20ppm
FN8099.1
September 15, 2005
23
X1227
A final application for the ATR control is in-circuit cali-
bration for high accuracy applications, along with a
temperature sensor chip. Once the RTC circuit is pow-
ered up with battery backup, the frequency drift is
measured. The ATR control is then adjusted to a set-
ting which minimizes drift. Once adjusted at a particu-
lar temperature, it is possible to adjust at other
discrete temperatures for minimal overall drift, and
store the resulting settings in the EEPROM. Extremely
low overall temperature drift is possible with this
method. The Intersil evaluation board contains the cir-
cuitry necessary to implement this control.
The X1 and X2 connections to the crystal are to be
kept as short as possible. A thick ground trace around
the crystal is advised to minimize noise intrusion, but
ground near the X1 and X2 pins should be avoided as
it will add to the load capacitance at those pins. Keep
in mind these guidelines for other PCB layers in the
vicinity of the RTC device. A small decoupling capaci-
tor at the Vcc pin of the chip is mandatory, with a solid
connection to ground.
For other RTC products, the same rules stated above
should be observed, but adjusted slightly since the
packages and pinouts are slightly different.
For more detailed operation see Intersil’s application
note AN154 on Intersil’s website at www.intersil.com.
Assembly
Most electronic circuits do not have to deal with
assembly issues, but with the RTC devices assembly
includes insertion or soldering of a live battery into an
unpowered circuit. If a socket is soldered to the board,
and a battery is inserted in final assembly, then there
are no issues with operation of the RTC. If the battery
is soldered to the board directly, then the RTC device
Vback pin will see some transient upset from either
soldering tools or intermittent battery connections
which can stop the circuit from oscillating. Once the
battery is soldered to the board, the only way to assure
the circuit will start up is to momentarily (very short
period of time!) short the Vback pin to ground and the
circuit will begin to oscillate.
Layout Considerations
The crystal input at X1 has a very high impedance and
will pick up high frequency signals from other circuits on
the board. Since the X2 pin is tied to the other side of
the crystal, it is also a sensitive node. These signals can
couple into the oscillator circuit and produce double
clocking or mis-clocking, seriously affecting the accu-
racy of the RTC. Care needs to be taken in layout of the
RTC circuit to avoid noise pickup. Below in Figure 19 is
a suggested layout for the X1226 or X1227 devices.
Figure 19. Suggested Layout for Intersil RTC in SO-8
Oscillator Measurements
When a proper crystal is selected and the layout guide-
lines above are observed, the oscillator should start up
in most circuits in less than one second. Some circuits
may take slightly longer, but startup should definitely
occur in less than 5 seconds. When testing RTC cir-
cuits, the most common impulse is to apply a scope
probe to the circuit at the X2 pin (oscillator output) and
observe the waveform. DO NOT DO THIS! Although in
some cases you may see a useable waveform, due to
the parasitics (usually 10pF to ground) applied with the
scope probe, there will be no useful information in that
waveform other than the fact that the circuit is oscillat-
ing. The X2 output is sensitive to capacitive impedance
so the voltage levels and the frequency will be affected
by the parasitic elements in the scope probe. Applying a
scope probe can possibly cause a faulty oscillator to
start up, hiding other issues (although in the Intersil
RTC’s, the internal circuitry assures startup when using
the proper crystal and layout). The best way to analyze
the RTC circuit is to power it up and read the real time
clock as time advances.
Backup Battery Operation
RTC products. 3.0V or 3.6V Lithium batteries are
appropriate, and sizes are available that can power a
Intersil RTC device for up to 10 years. Another option
Many types of batteries can be used with the Intersil
FN8099.1
24
September 15, 2005
X1227
is to use a supercapacitor for applications where Vcc
may disappear intermittently for short periods of time.
Depending on the value of supercapacitor used,
backup time can last from a few days to two weeks
(with >1F). A simple silicon or Schottky barrier diode
can be used in series with Vcc to charge the superca-
pacitor, which is connected to the Vback pin. Do not
use the diode to charge a battery (especially lithium
batteries!).
Figure 20. Supercapacitor charging circuit
2.7-5.5V
VCC
Vback
Supercapacitor
VSS
Since the battery switchover occurs at Vcc=Vback-
0.1V (see Figure 20), the battery voltage must always
be lower than the Vcc voltage during normal operation
or the battery will be drained. A second consideration
is the trip point setting for the system RESET- func-
tion, known as Vtrip. Vtrip is set at the factory at levels
for systems with either Vcc = 5V or 3.3V operation,
with the following standard options:
V
V
V
V
= 4.63V ± 3%
= 4.38V ± 3%
= 2.85V ± 3%
= 2.65V ± 3%
TRIP
TRIP
TRIP
TRIP
The summary of conditions for backup battery opera-
tion is given in Table 8:
Table 8. Battery Backup Operation
1. Example Application, Vcc = 5V, Vback = 3.0V
Condition
a. Normal Operation
Vcc
5.00
5.00
0-1.8
Vback
3.00
Vtrip
4.38
4.38
4.38
Iback
<<1µA
0
Reset
Notes
H
H
L
b. Vcc on with no battery
c. Backup Mode
0
1.8-3.0
<2µA
Timekeeping
only
2. Example Application, Vcc=3.3V,Vback=3.0V
Condition
a. Normal Operation
Vcc
3.30
3.30
0-1.8
Vback
3.00
Vtrip
2.65
2.65
2.65
Iback
<<1µA
0
Reset
H
H
L
b. Vcc on with no battery
c. Backup Mode
0
1.8-3.0*
<2µA*
Timekeeping
only
d. UNWANTED - Vcc ON, Vback
powering
2.65 - 3.30
> Vcc
2.65
up to 3mA
H
Internal
Vcc = Vback
*since Vback>2.65V is higher than Vtrip, the battery is powering the entire device
FN8099.1
September 15, 2005
25
X1227
Referring to Figure 20, Vtrip applies to the “Internal
Vcc” node which powers the entire device. This means
that if Vcc is powered down and the battery voltage at
Vback is higher than the Vtrip voltage, then the entire
chip will be running from the battery. If Vback falls to
lower than Vtrip, then the chip shuts down and all out-
puts are disabled except for the oscillator and time-
keeping circuitry. The fact that the chip can be
powered from Vback is not necessarily an issue since
standby current for the RTC devices is <2µA for this
mode (called “main timekeeping current” in the data
sheet). Only when the serial interface is active is there
an increase in supply current, and with Vcc powered
down, the serial interface will most likely be inactive.
PERFORMANCE DATA
Performance
I
BACK
IBACK vs. Temperature
Multi-Lot Process Variation Data
1.4
1.2
1.0
0.8
0.6
0.4
0.2
0
3.3V
1.8V
One way to prevent operation in battery backup mode
above the Vtrip level is to add a diode drop (silicon
diode preferred) to the battery to insure it is below
Vtrip. This will also provide reverse leakage protection
which may be needed to get safety agency approval.
-40
25
60
85
Temperature °C
One mode that should always be avoided is the opera-
tion of the RTC device with Vback greater than both Vcc
and Vtrip (Condition 2d in Table 8). This will cause the
battery to drain quickly as serial bus communication and
non-volatile writes will require higher supplier current.
FN8099.1
September 15, 2005
26
X1227
PACKAGING INFORMATION
8-Lead Plastic, SOIC, Package Code S8
0.150 (3.80) 0.228 (5.80)
0.158 (4.00) 0.244 (6.20)
Pin 1 Index
Pin 1
0.014 (0.35)
0.019 (0.49)
0.188 (4.78)
0.197 (5.00)
(4X) 7°
0.053 (1.35)
0.069 (1.75)
0.004 (0.19)
0.010 (0.25)
0.050 (1.27)
0.010 (0.25)
0.050"Typical
X 45°
0.020 (0.50)
0.050"
Typical
0° - 8°
0.0075 (0.19)
0.010 (0.25)
0.250"
0.016 (0.410)
0.037 (0.937)
0.030"
Typical
8 Places
FOOTPRINT
NOTE: ALL DIMENSIONS IN INCHES (IN PARENTHESES IN MILLIMETERS)
FN8099.1
27
September 15, 2005
X1227
PACKAGING INFORMATION
8-Lead Plastic, TSSOP, Package Code V8
.025 (.65) BSC
.169 (4.3)
.252 (6.4) BSC
.177 (4.5)
.114 (2.9)
.122 (3.1)
.047 (1.20)
.0075 (.19)
.0118 (.30)
.002 (.05)
.006 (.15)
.010 (.25)
Gage Plane
0° - 8°
Seating Plane
.019 (.50)
.029 (.75)
(7.72)
(4.16)
Detail A (20X)
(1.78)
(0.42)
.031 (.80)
.041 (1.05)
(0.65)
All Measurements Are Typical
See Detail “A”
NOTE: ALL DIMENSIONS IN INCHES (IN PARENTHESES IN MILLIMETERS)
All Intersil U.S. products are manufactured, assembled and tested utilizing ISO9000 quality systems.
Intersil Corporation’s quality certifications can be viewed at www.intersil.com/design/quality
Intersil products are sold by description only. Intersil Corporation reserves the right to make changes in circuit design, software and/or specifications at any time without
notice. Accordingly, the reader is cautioned to verify that data sheets are current before placing orders. Information furnished by Intersil is believed to be accurate and
reliable. However, no responsibility is assumed by Intersil or its subsidiaries for its use; nor for any infringements of patents or other rights of third parties which may result
from its use. No license is granted by implication or otherwise under any patent or patent rights of Intersil or its subsidiaries.
For information regarding Intersil Corporation and its products, see www.intersil.com
FN8099.1
28
September 15, 2005
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