RKC Instrument Inc CB900FJA3-M*NN-NN/A/Y, CB900FJ03-8*DN-N1/A/Y, CB900WK03-MM*AN-N1/A/Y, CB900FJA3-V*AN-N1/A/Y, CB100WJA3-MM*NN-N1/A/Y User manual

Digital Controller

CB100/CB400
CB500/CB700

CB900

[Z-1021]

MODBUS

Communication

Instruction Manual

RKC INSTRUMENT INC.

®

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IMCB14-E1

Modbus is a registered trademark of Schneider Electric.
Company names and product names used in this manual are the trademarks or registered trademarks of
the respective companies.

All Rights Reserved, Copyright 1999, RKC INSTRUMENT INC.

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Thank you for purchasing the RKC instrument. In order to achieve maximum performance and ensure
proper operation of your new instrument, carefully read all the instructions in this manual. Please
place this manual in a convenient location for easy reference.

SYMBOLS

WARNING

CAUTION

!

: This mark indicates precautions that must be taken if there is danger of electric

shock, fire, etc., which could result in loss of life or injury.

: This mark indicates that if these precautions and operating procedures are not

taken, damage to the instrument may result.

: This mark indicates that all precautions should be taken for safe usage.

: This mark indicates important information on installation, handling and operating

procedures.

: This mark indicates supplemental information on installation, handling and

operating procedures.

: This mark indicates where additional information may be located.

WARNING

!

An external protection device must be installed if failure of this instrument
could result in damage to the instrument, equipment or injury to personnel.

All wiring must be completed before power is turned on to prevent electric
shock, fire or damage to instrument and equipment.

This instrument must be used in accordance with the specifications to prevent
fire or damage to instrument and equipment.

This instrument is not intended for use in locations subject to flammable or
explosive gases.

Do not touch high-voltage connections such as power supply terminals, etc.
to avoid electric shock.

RKC is not responsible if this instrument is repaired, modified or
disassembled by other than factory-approved personnel. Malfunction can
occur and warranty is void under these conditions.

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CAUTION

This is a Class A instrument. In a domestic environment, this instrument may cause radio
interference, in which case the user may be required to take adequate measures.
This instrument is protected from electric shock by reinforced insulation. Provide
reinforced insulation between the wire for the input signal and the wires for instrument
power supply, source of power and loads.
This instrument is designed for installation in an enclosed instrumentation panel. All high­voltage connections such as power supply terminals must be enclosed in the
instrumentation panel to avoid electric shock by operating personnel.
All precautions described in this manual should be taken to avoid damage to the
instrument or equipment.
All wiring must be in accordance with local codes and regulations.
To prevent instrument damage or failure, protect the power line and the input/output lines
from high currents with a protection device such as fuse, circuit breaker, etc.
Prevent metal fragments or lead wire scraps from falling inside instrument case to avoid
electric shock, fire or malfunction.
Tighten each terminal screw to the specified torque found in the manual to avoid electric
shock, fire or malfunction.
For proper operation of this instrument, provide adequate ventilation for heat dispensation.
Do not connect wires to unused terminals as this will interfere with proper operation of the
instrument.
Turn off the power supply before cleaning the instrument.
Do not use a volatile solvent such as paint thinner to clean the instrument. Deformation or
discoloration will occur. Use a soft, dry cloth to remove stains from the instrument.
To avoid damage to instrument display, do not rub with an abrasive material or push front
panel with a hard object.

NOTICE

This manual assumes that the reader has a fundamental knowledge of the principles of electricity,
process control, computer technology and communications.
The figures, diagrams and numeric values used in this manual are only for purpose of illustration.
RKC is not responsible for any damage or injury that is caused as a result of using this instrument,
instrument failure or indirect damage.
Periodic maintenance is required for safe and proper operation of this instrument. Some
components have a limited service life, or characteristics that change over time.
Every effort has been made to ensure accuracy of all information contained herein. RKC makes no
warranty expressed or implied, with respect to the accuracy of the information. The information in
this manual is subject to change without prior notice.
No portion of this document may be reprinted, modified, copied, transmitted, digitized, stored,
processed or retrieved through any mechanical, electronic, optical or other means without prior
written approval from RKC.

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IMCB14-E1

CONTENTS

Page

1. OUTLINE ..............................................................................1

2. SPECIFICATIONS ................................................................2

3. WIRING.................................................................................3

4. COMMUNICATION SETTINGS............................................6

4.1 Communication Setting Mode .........................................................................6

4.2 Select Communication Parameters .................................................................7

4.3 Slave Address Setting .....................................................................................8

4.4 Communication Speed Setting......................................................................10

4.5 Data Configuration Setting ............................................................................12

4.6 Interval Time Setting .....................................................................................14

4.7 RS-485 Send/Receive Process Timing .........................................................17

5. MODBUS PROTOCOL.......................................................18

5.1 Message Format ...........................................................................................18

5.2 Function Code ...............................................................................................19

5.3 Communication Mode ...................................................................................19

5.4 Slave Response ............................................................................................20

5.5 Calculating CRC-16.......................................................................................21

6. MESSAGE FORMAT..........................................................23

6.1 Read Holding Registers [03H] .......................................................................23

6.2 Preset Single Registers [06H] .......................................................................24

6.3 Diagnostics (loopback test) [08H]..................................................................25

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Page

7. DATA CONFIGURATION....................................................26

7.1 Data Configuration ........................................................................................26

7.2 Data Processing Precautions ........................................................................27

7.3 Communication Data List ..............................................................................28

8. TROUBLESHOOTING .......................................................35

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1. OUTLINE

This manual describes the specifications, wiring instructions and communication settings for
CB100/CB400/CB500/CB700/CB900 Z-1021 with Modbus communication protocol.

Master side Slave side

Host computer

or PLC etc.

Host computer

or PLC etc.

RS-232C
MODBUS

RS-485

or

RS-232C/RS-485
converter

BRA-100B-2BRA-100-2

Junction
branch box

MODBUSMODBUS

MODBUS

MODBUS

MODBUS

CB100/CB400/CB500
CB700/CB900
(Slave address 1)

CB100/CB400/CB500
CB700/CB900
(Slave address 2)

CB100/CB400/CB500
CB700/CB900
(Slave address 3)

CB100/CB400/CB500
CB700/CB900
(Slave address 4)

CB100/CB400/CB500
CB700/CB900
(Slave address 31)

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1

2. SPECIFICATIONS

(1) Interface:

(2) Connection method:

(3) Protocol:

Based on RS-485, EIA standard

2-wire system, half-duplex multi-drop connection

Modbus

(4) Signal transmission mode: Remote Terminal Unit (RTU) mode

(5) Synchronous method: Start/stop synchronous type

(6) Communication speed: 2400 bps, 4800 bps, 9600 bps, 19200 bps

(Selectable)

(7) Data type:

bit)

(8) Function codes:

Data bit: 8 (Byte data corresponding to binary data or

Parity check : Without, Odd or Even (Selectable)
Stop bit: 1

03H (Read holding registers)
06H (Preset single register)
08H Diagnostics (loopback test)

(9) Error check method:

CRC-16

(10) Error codes: 1: Function code error

(Designation of an unsupported function code)

2: When written to read only data

When any address other than 0000H to 0019H is
specified, etc.

3: When the data written exceeds the setting range

When the specified number of data items in the query

message exceeds the maximum number of data items

available

4: Self-diagnostic error response

(11) Maximum connection: 32 instruments including a master

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3. WIRING

WARNING

!

To prevent electric shock or instrument failure, turn off the power before
connecting or disconnecting the instrument and peripheral equipment.

Terminal number and signal details

CB100/CB400/CB500/CB900

Terminal No. Signal name Name

13 SG Signal ground

14 T/R(A) Send data/Receive data

Slave Master

Signal direction

15 T/R(B) Send data/Receive data

CB700

Terminal No. Signal name Name

7 SG Signal ground

8 T/R(A) Send data/Receive data

9 T/R(B) Send data/Receive data

Signal direction

Slave Master

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3. WIRING

)

)

)

)

)

(

)

Connection to the RS-485 port of the master

The master has a built-in circuit to transfer send/receive data alternatively.

Paired wire

Master

SG
T/R(A

T/R(B

SD (TXD) and RD (RXD): Negative logic

SG

T/R(A)

T/R(B

Slave

SG

T/R(A

T/R(B

Slave

31 max.

RS-485

Shielded twisted

pair wire

Use a terminal resistor with a combined resistance of 100 on the last controller.

Connection to the RS-232C port of the master

A RS-232C/RS-485 communication converter is requited.

Paired wire

RS-485

SD (TXD)Send data

RD(RXD)Receive data

Send/Receive
transfer signal

SG

T/R(A)

T/R(B)

Slave

Shielded twisted

pair wire

Use a terminal resistor with a combined resistance of 100 on the last controller.

SG

T/R(A)

T/R(B)

RS-232C/RS-485

converter

RS-232C

Master

When the master uses Windows 95/NT, use a RS-232C/RS-485 converter with an automatic
send/receive transfer function.

Recommended: CD485, CD485/V manufactured by Data Link, Inc. or equivalent.

4

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Connection with up to 31 slaves and one master

3. WIRING

Master

RS-232C

RS-485

BRA-100B-2

RS-485

3029 311 2 3 4

SlavesSlavesSlaves

Slave address
example

Master

RS-485

BRA-100B-2

RS-232C/RS-485 converter

or

BRA-100B-2

For all pertinent details on the RS-232C/RS-485 converter and junction branch box (BRA­100B-2), see the respective instruction manuals.

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4. COMMUNICATION SETTINGS

To establish communication parameters between master and slave, it is necessary to set the slave
address, communication speed, data configuration and interval time on each slave in the
communication mode.
The CB900 controller will be used as an example, but the same instructions apply to all CB Series
controllers with Modbus protocol.

4.1 Communication Setting Mode

1. When the power to the instrument is turned on, the input type, input range and PV/SV display
mode will be automatically displayed in that order.

2. To go to the communication setting mode, you must be in either PV/SV display mode or the SV
setting mode. Press and hold the SET key and press the <R/S key at the same time to initiate
communication settings. The first parameter to be displayed will be the slave address, Add.

PV

SV

SET

ALM2ALM1AT OUT2OUT1

R/S

PV

SV

SET

ALM2ALM1AT OUT2OUT1

R/S

PV/SV display mode Communication setting mode

-Slave address setting

Add

The number segment being set will
be brighter than the others in the
SV display

To return to the PV/SV display mode, press and hold the SET key and press the <R/S key at
the same time.

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4. COMMUNICATION SETTINGS

4.2 Select Communication Parameters

To select parameters in communication setting mode, press the SET key. The parameters are
displayed and sequenced in the order of slave address, Add, communication speed, bPS, data
configuration, bIT and interval time set value, InT.

Display flowchart

Power On

Display changes automatically

Input type and input range
display

PV/SV display mode

Communication setting mode

PV

SV

PV

SV

PV

SV

(Display for approx. 4 sec)

Press the
SET key.

Press and hold the SET key and press the
<R/S key at same time.

Slave address
(Add)

Press the SET key.

Communication speed
(bPS)

Press the SET key.

Data configuration
(bIT)

SV setting mode

PV/SV display

mode

Press and hold the
SET key and press
the <R/S key at
same time.

Press the SET key.

PV

Press the
SET key.

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Interval time set value
(InT)

7

4. COMMUNICATION SETTINGS

4.3 Slave Address Setting

The slave address must be set before Modbus communication can begin. The slave address number
is set with numbers from 1 to 99. The factory set value is 0 and two-way communication is not
possible when the address is 0.

Symbol Name Setting range Description

Slave address 1 to 99* Set the controller slave

address.

Add

* Two-way communication is not possible when the address is 0.

When the communication parameter is changed, turn the power on and off again to refresh and
make the new value effective.

All slave address settings must be stored by pressing the SET key. If changes are made and
the SET key is not pressed within one minute, the display will automatically return to the
PV/SV display mode and the slave address will return to the value prior to set change.

Setting procedure

Example: Setting the slave address to 15

1. Go to the communication setting mode so that slave address, Add, is displayed.

Factory set

value

0

PV

SV

ALM2ALM1AT OUT2OUT1

SET

R/S

Slave address

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2. Press the UP key to enter 5 at the first digit from the right.

PV

SV

ALM2ALM1AT OUT2OUT1

SET

R/S

3. Press the <R/S key to high-light the second digit from the right.

4. COMMUNICATION SETTINGS

PV

SV

ALM2ALM1AT OUT2OUT1

SET

R/S

4. Press the UP key to enter 1 at the second digit form the right.

PV

SV

ALM2ALM1AT OUT2OUT1

SET

R/S

5. Press the SET key to store the new slave address. The display automatically goes to the next
communication parameter, bPS.

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4. COMMUNICATION SETTINGS

4.4 Communication Speed Setting

The communication speed of 2400bps, 4800bps, 9600bps or 19200bps is set with numbers from 0 to 3.
To change the number of the digit, press the UP or DOWN key.

Symbol Name Setting range Description

Communication
speed

0 : 2400 bps
1 : 4800 bps

Select the communication
speed

Factory set

value

2

2 : 9600 bps

bPS 3 : 19200 bps

Set the same communication speed for both the slave and the master.

When the communication parameter is changed, turn the power on and off again to refresh and
make the new value effective.

All communication speed settings must be stored by pressing the SET key. If changes are
made and the SET key is not pressed within one minute, the display will automatically return
to the PV/SV display mode and the communication speed will return to the value prior to set
change.

Setting procedure

Example: Setting the communication speed to 1: 4800 bps

1. Go to the communication setting mode so that slave address, Add, is displayed. Then, press the
SET key once, so the communication speed symbol, bPS, appears.

PV

SV

ALM2ALM1AT OUT2OUT1

SET

R/S

Communication speed

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4. SETTING FOR COMMUNICATION

2. Press the DOWN key to enter 1 (4800 bps) at the first digit from the right.

PV

SV

ALM2ALM1AT OUT2OUT1

SET R/S

3. Press the SET key to store the new communication speed. The display automatically goes to
the next communication parameter, bIT.

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4. SETTING FOR COMMUNICATION

4.5 Data Configuration Setting

The data configuration shown below is set with numbers from 1 to 3. To change the number of the
digit, press the UP or DOWN key.

Symbol Name Setting range Description

Data
configuration

bIT Configuration

Data configuration table

Setting Data bit Parity bit Stop bit

0 8 None 1

1 to 5 Do not set 1 to 5. Malfunction may result.

6 8 Even 1

7 8 Odd 1

Set the same data configuration for both the slave and the master.

0, 6 or 7

See Data

Table

Select data configuration
during communication

Factory set

value

0

12

When the communication parameter is changed, turn the power on and off again to refresh and
make the new value effective.

All data configuration settings must be stored by pressing the SET key. If changes are made
and the SET key is not pressed within one minute, the display will automatically return to the
PV/SV display mode and the data configuration will return to the value prior to set change.

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4. SETTING FOR COMMUNICATION

Setting procedure

Example: Setting the data configuration to 6: 8 data bits, even parity and 1 stop bit.

1. Go to the communication setting mode so that slave address, Add, is displayed. Press the SET
key until the data configuration symbol, bIT, appears.

PV

SV

ALM2ALM1AT OUT2OUT1

SET R/S

Data configuration

2. Press the UP key to enter 6 at the first digit from the right.

PV

SV

ALM2ALM1AT OUT2OUT1

SET

R/S

3. Press the SET key to store the new data configuration. The display automatically goes to the next
communication parameter, InT.

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4. SETTING FOR COMMUNICATION

4.6 Interval Time Setting

The interval time from 0 to 250 ms is set with numbers from 0 to 150. To shift the digit, press the
<R/S key. To change the number of the digit, press the UP or DOWN key.

Symbol Name Setting range Description

Interval time set
value

0 to 150* Set the value to set the interval

time

InT

* 0 to 250 ms can be set by using 0 to 150.

Formula to calculate interval time and interval time set value

Interval time = Interval time set value 1.666 ms
Interval time set value = Interval time

1.666 ms

When the communication parameter is changed, turn the power on and off again to refresh and
make the new value effective.

All interval times must be stored by pressing the SET key. If changes are made and the SET
key is not pressed within one minute, the display will automatically return to the PV/SV
display mode and the interval time will return to the value prior to set change.

Setting procedure

Example: Setting the interval time to 250 ms.

Factory set

value

5

1. Go to the communication setting mode so that slave address, Add, is displayed. Press the SET
key until the communication speed, InT, appears.

PV

SV

ALM2ALM1AT OUT2OUT1

SET

R/S

Interval time set value

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4. SETTING FOR COMMUNICATION

2. Calculate the interval time set value by using the formula on the previous page. The interval
time set value must be a whole number. If you get a number with a decimal fraction, round to
the nearest whole number.

Interval time set value:

250 ms 1.666 ms 150 (Round to the nearest whole number)
The actual interval time re-calculated by using the interval time set value, 150:
150 1.666 ms 249.9 (Approx. 250 ms)

Enter an interval time set value of 150, calculated as show above, on the controller.

3. Press the DOWN key to enter 0 at the first digit from the right.

PV

SV

ALM2ALM1AT OUT2OUT1

SET

R/S

4. Press the <R/S key to high-light the second digit from the right.

PV

SV

ALM2ALM1AT OUT2OUT1

SET

R/S

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4. SETTING FOR COMMUNICATION

5. Press the UP key to enter 5 at the second digit from the right.

PV

SV

SET

R/S

6. Press the <R/S key to high-light the third digit from the right.

ALM2ALM1AT OUT2OUT1

PV

SV

ALM2ALM1AT OUT2OUT1

SET

R/S

7. Press the UP key to enter 1 at the third digit from the right.

PV

SV

ALM2ALM1AT OUT2OUT1

SET

R/S

8. Press the SET key to store the new interval time. The display automatically goes back to the
communication parameter, Add.

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4. SETTING FOR COMMUNICATION

4.7 RS-485 Send/Receive Process Timing

The sending and receiving of RS-485 communication is conducted through two wires; consequently,
the transmission and reception of data requires precise timing. The following processing times are
required during data send/receive.

Slave process timing

Procedure details Time (ms)

Read holding registers [03H]

Response transmission time after the
slave
receives the query message

Preset single register [06H]

Response transmission time after the
slave
receives the query message

Diagnostics (loopback test) [08H]

Response transmission time after the
slave
receives the query message

13 ms max.

6 ms max.

6 ms max.

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5. MODBUS PROTOCOL

The master controls communication between master and slave. A typical message consists of a
request (query message) sent from the master followed by an answer (response message) from the
slave. When master begins data transmission, a set of data is sent to the slave in a fixed sequence.
When it is received, the slave decodes it, takes the necessary action, and returns data to the master.

5.1 Message Format

The message consists of four parts: slave address, function code, data, and error check code which are
always transmitted in the same sequence.

Slave address

Function code

Data

Error check CRC-16

Message format

Slave address

The slave address is a number from 1 to 99 manually set at the front key panel of the controller.
Although all connected slaves receive the query message sent from the master, only the slave with the
slave address coinciding with the query message will accept the message.

Function code

The function codes are the instructions set at the master and sent to the slave describing the action to
be executed. The function codes are included when the slave responds to the master.
For details, see 5.2 Function Code.

Data

The data to execute the function specified by the function code is sent to the slave and corresponding
data returned to the master from the slave.
For details, see 6. MESSAGE FORMAT, 7. DATA CONFIGURATION and 7.3 Communication
Data List.

Error check

An error checking code (CRC-16: Cyclic Redundancy Check) is used to detect an error in the signal
transmission. For the calculation method of CRC-16, see 5.5 Calculating CRC-16.

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5.2 Function Code

Function code contents

5. MODBUS PROTOCOL

Function code
(Hexadecimal)

03H

06H

08H

Message length of each function (Unit: byte)

Function code Function
(Hexadecimal)

03H

06H

08H

Read holding registers

Preset single register

Diagnostics (loopback test)

Read holding registers 8 8 7 255

Preset single register

Diagnostics (loopback test)

Function Contents

5.3 Communication Mode

Measured value (PV), alarm status, current
transformer input, etc.

Set value (SV), alarm set value, PID constants,
PV bias, etc. (For each word)

Diagnostics (loopback test)

Query message Response message

Min Max Min Max

8 8 8 8

8 8 8 8

Signal transmission between the master and slaves is conducted in Remote Terminal Unit (RTU)
mode.

RTU mode

Items Contents

Data bit length 8 bit (Binary)
Start mark of message Unused
End mark of message Unused
Message length
Data time interval 24 bit's time or less*
Error check CRC-16

* The data time intervals in one query message from the master must be 24 bit's time or less.

If the data time interval exceeds 24 bit's time, the slave regards the transmission as ended
and because the message format is incomplete, the slave does not respond.

See 5.2 Function Code

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5. MODBUS PROTOCOL

5.4 Slave Responses

(1) Normal response

In the response message of the Read Holding Registers, the slave returns the read out data and the
number of data items with the same slave address and function code as the query message.
In the response message of the Preset Single Register, the slave returns the same message as the
query message.
In the response message of the Diagnostics (loopback test), the slave returns the same message as
the query message.

(2) Defective message response

If the query message from the master is defective, except for transmission error, the slave returns
the error response message without any action.

Slave address

Function code

Error code

Error check CRC-16

Error response message

If the self-diagnostic function of the slave detects an error, the slave will return an error response
message to all query messages.
The function code of each error response message is obtained by adding 80H to the function code
of the query message.

Error code Contents

1

2

3

4

Function code error (Designation of an unsupported function code)
When written to read only data
When any address other than 0000H to 0019H is specified
When PID constants or anti-reset windup (ARW) data are set to 0 and 1 is
entered at self-tuning (ST) function
When either one of PID constants and anti-reset windup (ARW) data are written
during execution of the self-tuning (ST) function

When the data written exceeds the setting range
When the specified number of data items in the query message exceeds the
maximum number of data items available

Self-diagnostic error response

(3) No response

The slave ignores the query message and does not respond when:

The slave address in the query message does not coincide with any slave address settings.
The transmission parameter of the master does not coincide with that of the slave.
Transmission error such as overrun, framing, parity and etc., is found in the query message.
Data time interval in the query message from the master exceeds 24 bit's time.

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5. MODBUS PROTOCOL

5.5 Calculating CRC-16

The Cyclic Redundancy Check (CRC) is a 2 byte (16-bit) error check code. After constructing the
data message, not including start, stop, or parity bit, the master calculates a CRC code and appends
this to the end of the message. The slave will calculate a CRC code from the received message, and
compare it with the CRC code from the master. If they do not coincide, a communication error has
occurred and the slave does not respond.

The CRC code is formed in the following sequence:

1. Load a 16-bit CRC register with FFFFH.

2. Exclusive OR ( ) the first byte (8 bits) of the message with the CRC register. Return the result to

the CRC register

3. Shift the CRC register 1 bit to the right.

4. If the carry flag is 1, exclusive OR the CRC register with A001 hex and return the result to the

CRC register. If the carry flag is 0, repeat step 3.

5. Repeat step 3 and 4 until there have been 8 shifts.

6. Exclusive OR the next byte (8 bits) of the message with the CRC register..

7. Repeat step 3 through 6 for all bytes of the message (except the CRC).

8. The CRC register contains the 2 byte CRC error code. When they are appended to the message,

the low-order byte is appended first, followed by the high-order byte.

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21

5. MODBUS PROTOCOL

The flow chart of CRC-16

START

FFFFH CRC Register

CRC Register next byte of the message CRC Register

0 n

Shift CRC Register right 1 bit

Carry flag is 1

Yes

CRC Register A001H CRC Register

n + 1 n

No

No

n 7

Yes

Is message
complete ?

Yes

END

No

The symbol indicates an exclusive OR operation.
The symbol for the number of data bits is n.

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6. MESSAGE FORMAT

6.1 Read Holding Registers [03H]

The query message specifies the starting register address and quantity of registers to be read.
The contents of the holding registers are entered in the response message as data, divided into two
parts: the high-order 8 bits and the low-order 8 bits, arranged in the order of the register numbers.

Example: The contents of the three holding registers from 0000H to 0002H are the read out from
slave address 2.

Query message

Slave address 02H

Function code 03H

Starting number High 00H

Low 00H

Quantity High 00H

Low 03H

CRC-16 High 05H

Low F8H

First holding register address

The setting must be between 1 and 125
(0001H and 007DH)

Normal response message

Slave address 02H

Function code 03H

Number of data 06H

First holding High 00H

register contents Low 64H

Next holding High 00H

register contents Low 00H

Next holding High 00H

register contents Low 00H

CRC-16 High 44H

Low 4DH

Error response message

Slave address 02H

80H Function code 83H

Error code 03H

CRC-16 High F1H

Low 31H

Number of holding registers 2

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23

6. MESSAGE FORMAT

6.2 Preset Single Register [06H]

The query message specifies data to be written into the designated holding register. The write data
is arranged in the query message with high-order 8 bits first and low-order 8 bits next. Only R/W
holding registers can be specified.

Example: Data is written into the holding register 0006H of slave address 1.

Query message

Slave address 01H

Function code 06H

Holding register High 00H

number Low 06H

Write data High 00H

Low C8H

CRC-16 High 68H

Low 5DH

Any data within the range

Normal response message

Slave address 01H

Function code 06H

Holding register High 00H

number Low C6H

Write data High 00H

Low 08H

CRC-16 High 68H

Low 5DH

Error response message

Slave address 01H

80H Function code 86H

Error code 02H

CRC-16 High C3H

Low A1H

Contents will be the same as query message data.

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IMCB14-E1

6. MESSAGE FORMAT

6.3 Diagnostics (Loopback Test) [08H]

The master's query message will be returned as the response message from the slave. This function
checks the communication system between the master and slave.

Example: Loopback test for slave address 1

Query message

Slave address 01H

Function code 08H

Test code High 00H

Low 00H

Data High 1FH

Low 34H

CRC-16 High E9H

Low ECH

Test code must be set to 00

Any pertinent data

Normal response message

Slave address 01H

Function code 08H

Test code High 00H

Low 00H

Data High 1FH

Low 34H

CRC-16 High E9H

Low ECH

Error response message

Slave address 01H

80H Function code 88H

Error code 03H

CRC-16 High 06H

Low 01H

Contents will be the same as query message data.

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25

7. DATA CONFIGURATION

7.1 Data Configuration

The numeric range of data used in Modbus protocol is 0000H to FFFFH. Only the set value within
the setting range is effective.

FFFFH represents -1.

Data processing with decimal points

Data with decimal points

The Modbus protocol does not recognize data with decimal points during communication.

Data with one decimal place

Current transformer input 1 Heater break alarm 1
Current transformer input 2 Heater break alarm 2
(Z-168 specification) (Z-168 specification)
Control loop break alarm

Example: When heater break alarm (HBA) 1 set value is 20.0 A; 20.0 is processed as 200, 200 =
00C8H

Heater break alarm 1 High 00H

Low C8H

Data without decimal points

Alarm 1 status Derivative time
Alarm 2 status Anti-reset windup
Burnout Heat-side proportioning cycle time
LBA deadband Cool-side proportional band
Autotuning (AT) Cool-side proportioning cycle time
Self-tuning (ST) Set data lock function
Integral time RUN/STOP function

Example: When integral time is 50 seconds, 50 is processed as 50, 50 = 0032H

Integral time High 00H

Low 32H

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IMCB14-E1

7. DATA CONFIGURATION

Data whose decimal point's presence and/or position depends on input
range

The position of the decimal point changes depending on the input range type because the Modbus
protocol does not recognize data with decimal points during communication.
The following data can have one of three decimal point positions:

No decimal point
One decimal place

Two decimal places
The input range for voltage/current input is fixed at 0.0 to 100.0%. For details, see Input Range
Table 2 on P.34.

Measured value (PV) Heat-side proportional band
Set value (SV) Deadband
Alarm 1 set value PV bias
Alarm 2 set value

Example: When the temperature set value is -20.0 C; -20.0 is processed as -200,

-200 = 0000H - 00C8H = FF38H

Set value (SV) High FFH

Low 38H

7.2 Data Processing Precautions

For 03H (data read from the holding register), an error response message is returned when any
address other than 0000H to 0019H is specified as the starting number.

For 06H (data write to the single holding register), an error response message is returned when
data is written to any address other than 0000H to 0019H.

Read data of unused channel and undefined address is 0.

Any attempt to write to an unused channel is not processed as an error. Data can not be written
into an unused channel.

If data range or address error occurs during data writing, the data written before error is in effect.

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7. DATA CONFIGURATION

y

7.3 Communication Data List

The communication data list summarizes data addresses (holding register numbers), names, attributes,
setting ranges and factory set values.

(Attribute RO: Read only R/W: Read and Write)

*1

Attrib-

ute

RO 0.0 to 100.0 A -

Data range or item description

Process alarm, deviation alarm, SV
alarm:

-1999 to +9999 C [ F] or

-199.9 to +999.9 C [ F]

Deviation alarm: -span to +span
(Within 9999)
Process alarm, SV alarm:
Within input range

(0.0 can not be set.)

0 to 9999 C [ F]
Voltage/current inputs:
0 to 100 % of span

suspension
1: Autotuning (AT) start*
*After AT is completed, setting will
automatically change to 0

1: Self-tuning (ST) start

Continued on the next page.

Address Name

00H Measured value (PV) RO Within input range -

01H Current transformer input 1 RO 0.0 to 100.0 A -

02H Current transformer input 2

03H Alarm 1 status RO 0: OFF 1: ON -

04H Alarm 2 status RO 0: OFF 1: ON -

05H Burnout RO 0: OFF 1: ON -

06H Set value (SV) R/W Within input range 0

07H Alarm 1 set value R/W Temperature input:

08H Alarm 2 set value Voltage/current inputs:

09H Heater break alarm 1 R/W 0.0 to 100.0 A 0.0

0AH Heater break alarm 2 *2 R/W 0.0 to 100.0 A 0.0

0BH Control loop break alarm R/W 0. 1 to 200.0 min.

0CH LBA deadband R/W Temperature input:

0DH Autotuning (AT) R/W 0: Autotuning (AT) end or

0EH Self-tuning (ST) *3 R/W 0: Self-tuning (ST) suspension

Factor

set value

Temperature
input:
50 or 50.0

Voltage/
current
inputs:

5.0

8.0

0

0

0

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Continued from the previous page.

y

Address Name

Attrib-

ute

7. DATA CONFIGURATION

(Attribute RO: Read only R/W: Read and Write)

Data range or item description

Factor

set value

0FH Heat-side proportional band

(P) *4

10H Integral time (I) *4 R/W 1 to 3600 sec (0: PD control)

11H Derivative time (D) *4 R/W 1 to 3600 sec (0: PI control)

12H Anti-reset windup (ARW)

13H Heat-side proportioning

cycle time

14H Cool-side proportional

band

15H Deadband R/W Temperature input:

16H Cool-side proportioning

cycle time

17H PV bias R/W -span to +span

R/W Temperature input: 1 (0.1) to span or

9999 (999.9) C [ F]
Voltage/current inputs:

0.1 to 100.0 % of span
(ON/OFF action control when set to
0 or 0.0.)

Can not be set while the self-tuning
(ST) function is On

Can not be set while the self-tuning
(ST) function is On

Can not be set while the self-tuning
(ST) function is On

R/W 1 to 100 % of heat-side proportional

*4

R/W 1 to 100 sec (0 can not be set.)

R/W 1 to 1000% of heat-side proportional

R/W 1 to 100 sec (0 can not be set.)

band (0: Integral action OFF)

Can not be set while the self-tuning
(ST) function is On

Can not be set if the control output
is current output.

band (0 can not be set.)

-10 to +10 C [ F] or

-10.0 to +10.0 C [ F]
Voltage/current inputs:

-10.0 to +10.0 % of span

Can not be set if the control output
is current output.

However, temperature inputs:

-1999 to +1999 C [ F] or

-199.9 to 999.9 C [ F]

Continued on the next page.

Temperature
input:
30 (30.0)

Voltage/
current
inputs:

3.0

240

60

100

*5

100

0 or 0.0

*6

0 or 0.0

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7. DATA CONFIGURATION

y

Continued from the previous page.

(Attribute RO: Read only R/W: Read and Write)

Address Name

18H Set data lock function R/W 0 to 7 *7 0

19H RUN/STOP function R/W 0: RUN 1: STOP 0

*1 For the current transformer input 2 function, Z-168 specification is required.

*2 For a unit without Z-168 specification, the read data is 0.

*3 When heating proportional band (P), integral time (I), derivative time (D) or anti-reset windup

(ARW) is set to 0, self-tuning (ST) cannot be set to 1, self-tuning start. Error code 2 is sent.

*4 The heat-side proportional band (P), integral time (I), derivative time (D) and anti-reset windup

(ARW) cannot be set while the self-tuning (ST) function is being executed. Error code 2 is
sent.

Attrib-

ute

Data range or item description

Factor

set value

*5 Relay contact output: 20 sec

Voltage pulse output, trigger output for triac driving, triac output: 2 sec

*6 Relay contact output: 20 sec

Voltage pulse output, triac output: 2 sec

*7 Details of set data lock selection.

Set data Set value (SV) Alarm setting set value

(Alarm 1, Alarm 2)

0
1 ­2 ­3 - ­4 ­5 - ­6 - ­7 - - -

(-) Unsettable-Data locked ( ) Settable-Data unlocked

The data lock function only prevents setting changes being made from the front keys. Setting
changes can still be made through communication transmission.

Other setting items

Reading RO (read only) and R/W (read/write) unused data are not processed as an error at
read holding registers, but read data will be 0.

Any attempt to write unused data is not processed as an error. Data can not be written into
the slave.

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IMCB14-E1

7. DATA CONFIGURATION

Input Range Tables

Input Range Table 1

Input type Input range Code

Input Range

0 to 200 C K 01

0 to 400 C K 02

0 to 600 C K 03

0 to 800 C K 04

0 to 1000 C K 05

0 to 1200 C K 06

0 to 1372 C K 07

K 0 to 100 C K 13

0 to 300 C K 14

0 to 450 C K 17

0 to 500 C K 20

0 to 800 F K A1

0 to 1600 F K A2

0 to 2502 F K A3

20 to 70 F K A9

0 to 200 C J 01

0 to 400 C J 02

0 to 600 C J 03

0 to 800 C J 04

Thermocouple 0 to 1000 C J 05

(TC) J 0 to 1200 C J 06

0 to 450 C J 10

0 to 800 F J A1

0 to 1600 F J A2

0 to 2192 F J A3

0 to 400 F J A6

0 to 300 F J A7

0 to 1600 C *1 R 01

0 to 1769 C *1 R 02

R 0 to 1350 C *1 R 04

0 to 3200 F *1 R A1

0 to 3216 F *1 R A2

0 to 1600 C *1 S 01

S 0 to 1769 C *1 S 02

0 to 3200 F *1 S A1

0 to 3216 F *1 S A2

Continued on the next page.

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7. DATA CONFIGURATION

Continued from the previous page.

Input type Input range Code

Input Range

0 to 800 C E 01

E 0 to 1000 C E 02

0 to 1600 F E A1

0 to 1832 F E A2

0 to 1200 C N 01

N 0 to 1300 C N 02

0 to 2300 F N A1

0 to 2372 F N A2

-199.9 to +400.0 C *2 T 01

-199.9 to +100.0 C *2 T 02

-100.0 to +200.0 C T 03

0.0 to 350.0 C T 04

T -199.9 to +752.0 F *2 T A1

-100.0 to +200.0 F *2 T A2

-100.0 to +400.0 F *2 T A3

Thermocouple 0.0 to 450.0 F T A4

(TC) 0.0 to 752.0 F T A5

0 to 1300 C A 01

0 to 1390 C A 02

PL II 0 to 1200 C A 03

0 to 2400 F A A1

0 to 2534 F A A2

-199.9 to +600.0 C *2 U 01

-199.9 to +100.0 C *2 U 02

U 0.0 to 400.0 C U 03

-199.9 to +999.9 F *2 U A1

-100.0 to +200.0 F *2 U A2

0.0 to 999.9 F U A3

0 to 400 C L 01

L 0 to 800 C L 02

0 to 800 F L A1

0 to 1600 F L A2

Continued on the next page.

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7. DATA CONFIGURTION

Continued from the previous page.

Input type Input range Code

-199.9 to +649.0 C D 01

-199.9 to +200.0 C D 02

-100.0 to +50.0 C D 03

-100.0 to +100.0 C D 04

-100.0 to +200.0 C D 05

0.0 to 50.0 C D 06

0.0 to 100.0 C D 07

0.0 to 200.0 C D 08

0.0 to 300.0 C D 09

Pt100 0.0 to 500.0 C D 10

-199.9 to +999.9 F D A1

-199.9 to +400.0 F D A2

-199.9 to +200.0 F D A3

RTD -100.0 to +100.0 F D A4

-100.0 to +300.0 F D A5

0.0 to 100.0 F D A6

0.0 to 200.0 F D A7

0.0 to 400.0 F D A8

0.0 to 500.0 F D A9

-199.9 to +649.0 C P 01

-199.9 to +200.0 C P 02

-100.0 to +50.0 C P 03

-100.0 to +100.0 C P 04

JPt100 -100.0 to +200.0 C P 05

0.0 to 50.0 C P 06

0.0 to 100.0 C P 07

0.0 to 200.0 C P 08

0.0 to 300.0 C P 09

0.0 to 500.0 C P 10

*1 Accuracy is not guaranteed between 0 to 399 C (0 to 799 F).
*2 Accuracy is not guaranteed between -199.9 to -100.0 C (-199.9 to -158.0 F).

Input Range

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7. DATA CONFIGURATION

Input Range Table 2

Input type Input range Code

Input Range

Voltage input DC 0 to 5 V 4 01

(V) DC 0 to 10 V* 5 01

DC 1 to 5 V 0. 0 to 100.0 % 6 01

Current input DC 0 to 20 mA 7 01

(mA) DC 4 to 20 mA 8 01

* For this voltage range, Z-1010 specification is required.

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IMCB14-E1

8. TROUBLESHOOTING

WARNING

!

To prevent electric shock or instrument failure, always turn off the system
power before replacing the instrument.

To prevent electric shock or instrument failure, always turn off the power
before mounting or removing the instrument.

To prevent electric shock or instrument failure, do not turn on the power until
all the wiring is completed.

To prevent electric shock or instrument failure, do not touch the inside of the
instrument.

All wiring must be performed by authorized personnel with electrical
experience in this type of work.

This section lists some basic causes and solutions for Modbus communication problems.
If you can not find a solution, contact your nearest RKC sales office or agent for additional
information about replacement or repair.

Symptom Probable cause Solution

No response The controller power is not turned on Turn on the power

There communication cable is improperly
connected

Breakage in the communication cable Replace the cable

Detachment of the communication cable Confirm the connection condition

Problems with the connectors or contacts Check and replace the wiring in the

The communication speed or bit structure
settings are different

The address specification is different Confirm the address numbers

A transmission error (overrun error, framing
error, parity error or CRC-16 error) is found in
the query message

The time interval between adjacent data in the
query message is too long, exceeding 24 bit's
time

Instrument failure

Confirm the connection method

connector
Confirm each setting

Re-transmit after time-out occurs or
verify communication program

Replace instrument or return for
repair

Continued on the next page.

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8. TROUBLESHOOTING

Continued from the previous page.

Symptom Probable cause Solution

Error code 1 Function code error

(An unsupported function code was
specified)

Error code 2 Written to read only data. Confirm the address of holding

Any address other than 0000H to 0019H
is specified.

PID constants or anti-reset windup
(ARW) data are set to 0 and 1 is entered
at self-tuning (ST) function

Either one of PID constants and anti-reset
windup (ARW) data are written during
execution of the self-tuning (ST) function.

Error code 3 The data written exceeds the setting

range.

When the specified number of data items
in the query message exceeds the
maximum number of data items available.

Error code 4 Self-diagnostic error Turn off the power to the instrument.

Confirm the function code

register

Set the PID constants and anti-reset
windup (ARW) data to any number
other than 0.

Set the self-tuning (ST) function to 0.

Confirm the setting data

Re-set the data within the range of 1
to 125 (0000H to 007DH).

If the same error occurs when the
power is turned back on, contact your
nearest RKC sales office or agent.

36

Error codes 1 to 4 indicate that an error response message has been transmitted.

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