N8100Z2100 [ETC]

CONTROLLER ; 控制器\n


型号：	N8100Z2100
厂家：	ETC
描述：	CONTROLLER 控制器\n 控制器
文件：	总9页 (文件大小：725K)
中文：	中文翻译
下载：	下载PDF数据表文档文件

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INTRODUCTION

This document specifies the MODBUS communications protocol as implemented

on the -DIN, -DIN and ₁₆-DIN Temperature Controllers.

Certain restrictions have been imposed upon this implementation:

(i) Baud rates may be set to 1200, 2400, 4800 and 9600 only

(ii) Support for multi-parameter Writes is limited to support of the Multi-word

Write Function (Number 16) but will permit writing of one parameter only per

message

(iii) The multi-parameter Read function supports a maximum of 10

parameters in one message.

MODBUS FUNCTIONS SUPPORTED

In the following list, the original Gould MODBUS function names have been used,

followed by the JBUS names in italics, where such an equivalence exists. The

MODBUS Function number follows the names.

Read Coil Status (Read n Bits)

01/02

03/04

Read Holding Registers (Read n Words)

Force Single Coil (Write 1 Bit)

Preset Single Register (Write 1 Word)

Loopback Diagnostic Test

Preset Multiple Registers (Write n Words)

The instrument will identify itself in reply to a Read Holding Registers message

which enquires the values of parameter numbers 121 & 122, as specified in the

CNOMO documentation, and MODBUS Function 17 (Report Slave ID) is not

supported.

MESSAGE FORMATS

The first character of every message is an instrument address. The valid range of

such an address is 0 to 255. The second character is always the Function

Number. The contents of the remainder of the message depends upon the

function number.

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In most cases the instrument is required to reply by echoing the address and

function number, together with an echo of all or part of the message received (in

the case of a request to write a value or carry out a command) or the information

requested (in the case of a read parameter operation). Broadcast Messages (to

which the controller responds by taking some action without sending back a

reply) are supported at instrument address zero. Commands which can be

broadcast are marked with the symbol B.

Data is transmitted as eight-bit binary bytes with 1 start bit, 1 stop bit and optional

parity checking (None, Even or Odd).

A message is terminated solely by a delay of more than three character lengths

at the given Baud Rate, and any character received after such a delay is treated

as a potential address at the start of a new message.

The following individual message formats apply. Since only the RTU form of the

protocol is supported, each message is followed by a two-byte CRC16. Details of

how the checksum must be calculated are given at the end of this Section.

Read Coil Status (Read n Bits)

01/02

The message sent to the controller will consist of 8 bytes, as follows:

The normal reply will echo the first two characters of the message received, and

will then contain a single-byte data byte count, which will not include itself or the

CRC. For this message, there will be one byte of data per eight bits-worth of

information requested, with the LSbit of the first data byte transmitted depicting

the state of the lowest-numbered bit required.

This function will be used largely to report controller status information, and so a

bit set to 1 indicates that the corresponding feature is currently enabled/active,

and a bit reset to 0 indicates the opposite. If an exact multiple of eight bits is not

requested, the data is padded with trailing zeros to preserve the 8-bit format.

After the data has been transmitted, the CRC16 value is sent.

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Read Holding Registers (Read n Words)

03/04

The message sent to the controller to obtain the value of one or more registers is

an eight-byte message as follows:

The reply sent by the controller echoes the first 2 characters received and then

contains a single-byte data byte count, the value of which does not include either

itself or the CRC value to be sent. For this message, the count equals the number

of parameters read times two. Following the byte count, that number of

parameter values are transmitted, MSB first, followed by the CRC16.

Force Single Coil (Write 1 Bit)

05 B

The message received by the controller is 8 bytes long, consisting of the standard

preamble and the address of the bit to force, followed by a two-byte word whose

MSB contains the desired truth value of the bit expressed as 0xFF (TRUE) or 0x00

(FALSE).

Generally, this function will be used to control such features as Auto/Manual and

Tuning. The normal reply sent by the controller will be a byte-for-byte echo of the

message received.

Preset Single Register (Write 1 Word)

06 B

The message sent to the controller consists of 8 bytes: the address and function

number as usual, the address of the parameter to be written, and the two-byte

value to which the parameter will be set, and finally the CRC16.

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The normal response is to echo the message in its entirety.

Loopback Diagnostic Test

The controller is sent an 8 byte message consisting of the usual preamble, a

two-byte diagnostic code, and two bytes of data, followed by the CRC16.

Full MODBUS support in this area is not appropriate - consequently, the only

Diagnostic Code supported is code 00. In response to the message, the

controller must echo the message received exactly.

Preset Multiple Registers (Write n Words) 16 B

This message consists of eleven bytes. Only one parameter may be written at a

time, even though this function number is supported. The preamble is followed by

the address of the parameter to be written, and then a two-byte word count

(always set to 1) and a single-byte byte count (always set to 2). Finally, the value

to be written is followed by the CRC16.

The controller normally responds with a eight-byte reply, as follows:

Error and Exception Responses

If the controller receives a message which contains a corrupted character (parity

check fail, framing error etc.), or if the CRC16 check fails, the controller ignores

the message. If the message is otherwise syntactically flawed (e.g. the byte count

or word count is incorrect) the controller will also not reply.

However, if the controller receives a syntactically correct message which

nonetheless contains an illegal value, it will send an exception response,

consisting of five bytes as follows:

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The Function Number field consists of the function number contained in the

message which caused the error, with its top bit set (i.e. function 3 becomes

0x83), and the Exception Number is one of the codes contained in the following

table:

Code

Name

ILLEGAL FUNCTION

ILLEGAL DATA ADDRESS

ILLEGAL DATA VALUE

DEVICE FAILURE

Cause

Function Number out of range

Parameter ID out of range or not supported

Attempt to write invalid data/action not carried out

N/A

ACKNOWLEDGE

BUSY

NEGATIVE ACKNOWLEDGE

CRC16 Calculation

This is a 16-bit cyclic redundancy checksum. It is calculated in accordance with

a formula which involves recursive division of the data by a polynomial, with the

input to each division being the remainder of the results of the previous one.

The formula specifies that input is treated as a continuous bit-stream binary

number, with the most significant bit being transmitted first. However, the

transmitting device sends the least significant bit first.

According to the formula, the dividing polynomial is 2 ¹⁶+ 2¹⁵+ 2²+ 1 (Hex

18005), but this is modified in two ways:

i. Because the bit-order is reversed, the binary pattern is reversed also,

making the MSB the rightmost bit, and

ii. Because only the remainder is of interest, the MSB (the rightmost bit) may

be discarded.

This means the polynomial has the value Hex A001. The CRC algorithm is as shown

overleaf:

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PARAMETER NUMBERS

The parameter numbering system, in order to conform to the CNOMO standard,

splits parameters into BITS and WORDS and numbers each group independently.

Bit Parameters (Controller Status Byte)

There are a maximum of sixteen of these:

No.

Parameter

Communications Write Status

Auto/Manual Control

Self-Tune Status

Pre-Tune Status

Alarm 1 Status

Alarm 2 Status

Setpoint Ramp Enable(d)

Reserved

Notes

Read only - 1 = enabled, 0 = disabled

1 = Manual, 0 = Auto

1 = active, 0 = inactive

Read only - 1 = active, 0 = inactive

1 = enable(d), 0 = disable(d)

Reserved

Loop Alarm Enable(d)

Reserved

1 = enable(d), 0 = disable(d)

Reserved

Word Parameters

No.

Parameter

Process Variable

Notes

Read only

Setpoint

Target setpoint, if ramping

Read only, unless in Manual Control

Read only

Output Power

Arithmetic Deviation

Proportional Band 2

Proportional Band 1

Control action (direct/reverse)

Reset (or Loop Alarm Time)

Rate

Read only, if Self-tuning

Output 1 Cycle Time

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No.

Parameter

Scale Range Low

Notes

Read only if non-linear input

Scale Range High

Alarm 1 value

Alarm 2 value

Manual Reset

Overlap/Deadband

ON/OFF Differential

Decimal Point Position

Output 2 Cycle Time

Output 1 Power Limit

Internal setpoint

Read only if non-linear input

Read only - current value

Setpoint High Limit

Setpoint Low Limit

Setpoint Ramp Rate

Input Filter Time Constant

Process Variable Offset

Recorder Output Max.

Recorder Output Min.

Some of the parameters which do not apply to a particular instrument

configuration (e.g. Proportional Band 2 on a single output instrument) will accept

reads & writes. Others will accept reads only, and will return an exception if an

attempt is made to write values to them. The values read will in all cases be

undefined. It is the user’s responsibility to make sure that values read reflect a

possible state of the instrument.

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