RKC INSTRUMENT CB100 Series Use and care manual

IMCB14-E1
CB100/CB400
CB500/CB700
CB900
[Z-1021]
MODBUS
Communication
Instruction Manual
RKC INSTRUMENT INC.
®
Digital Controller

All Rights Reserved, Copyright ¤1999, RKC INSTRUMENT INC.
zModbus is a registered trademark of Schneider Electric.
zCompany names and product names used in this manual are the trademarks or registered trademarks of
the respective companies.

IMCB14-E1 i-1
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
: 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.
z
An external protection device must be installed if failure of this instrument
could result in damage to the instrument, equipment or injury to personnel.
z
All wiring must be completed before power is turned on to prevent electric
shock, fire or damage to instrument and equipment.
z
This instrument must be used in accordance with the specifications to prevent
fire or damage to instrument and equipment.
z
This instrument is not intended for use in locations subject to flammable or
explosive gases.
z
Do not touch high-voltage connections such as power supply terminals, etc.
to avoid electric shock.
z
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.
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.
WARNING
!
WARNING
!

IMCB14-E1
i-2
zThis 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.
zThis 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.
zThis instrument is designed for installation in an enclosed instrumentation panel. All high-
voltage connections such as power supply terminals must be enclosed in the
instrumentation panel to avoid electric shock by operating personnel.
zAll precautions described in this manual should be taken to avoid damage to the
instrument or equipment.
zAll wiring must be in accordance with local codes and regulations.
zTo 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.
zPrevent metal fragments or lead wire scraps from falling inside instrument case to avoid
electric shock, fire or malfunction.
zTighten each terminal screw to the specified torque found in the manual to avoid electric
shock, fire or malfunction.
zFor proper operation of this instrument, provide adequate ventilation for heat dispensation.
zDo not connect wires to unused terminals as this will interfere with proper operation of the
instrument.
zTurn off the power supply before cleaning the instrument.
zDo 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.
zTo avoid damage to instrument display, do not rub with an abrasive material or push front
panel with a hard object.
NOTICE
zThis manual assumes that the reader has a fundamental knowledge of the principles of electricity,
process control, computer technology and communications.
zThe figures, diagrams and numeric values used in this manual are only for purpose of illustration.
zRKC is not responsible for any damage or injury that is caused as a result of using this instrument,
instrument failure or indirect damage.
zPeriodic maintenance is required for safe and proper operation of this instrument. Some
components have a limited service life, or characteristics that change over time.
zEvery 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.
zNo 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.
CAUTION

IMCB14-E1 i-3
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

IMCB14-E1
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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

IMCB14-E1 1
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.
CB100/CB400/CB500
CB700/CB900
(Slave address 1)
RS-485
MODBUSMODBUS
CB100/CB400/CB500
CB700/CB900
(Slave address 2)
MODBUS
BRA-100B-2BRA-100-2
CB100/CB400/CB500
CB700/CB900
(Slave address 3)
MODBUS
CB100/CB400/CB500
CB700/CB900
(Slave address 4)
MODBUS
or
RS-232C
MODBUS
CB100/CB400/CB500
CB700/CB900
(Slave address 31)
RS-232C/RS-485
converter
Junction
branch box

2IMCB14-E1
2. SPECIFICATIONS
(1) Interface: Based on RS-485, EIA standard
(2) Connection method: 2-wire system, half-duplex multi-drop connection
(3) Protocol: 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: Data bit: 8 (Byte data corresponding to binary data or
bit)
Parity check : Without, Odd or Even (Selectable)
Stop bit: 1
(8) Function codes: 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

IMCB14-E1 3
3. WIRING
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

Terminal number and signal details
CB100/CB400/CB500/CB900
Terminal No. Signal name Name Signal direction
Slave Master
13 SG Signal ground
14 T/R(A) Send data/Receive data
15 T/R(B) Send data/Receive data
CB700
Terminal No. Signal name Name Signal direction
Slave Master
7 SG Signal ground
8 T/R(A) Send data/Receive data
9 T/R(B) Send data/Receive data
To prevent electric shock or instrument failure, turn off the power before
connecting or disconnecting the instrument and peripheral equipment.
WARNING
!

3. WIRING
IMCB14-E1
4



Connection to the RS-485 port of the master
The master has a built-in circuit to transfer send/receive data alternatively.
SG
T/R
(
B
)
T/R
(
A
)
SG
T/R
(
B
)
T/R
(
A
)
RD
(
RXD
)
：
Receive data
SD
(
TXD
)
：
Send data
Master
RS-485
SG
T/R
(
B
)
T/R
(
A
)
y
y
y
(
31 max.
)
Paired wire
Send/Receive
transfer signal
Shielded twisted
pair wire
Use a terminal resistor with a combined resistance of 100 :on the last controller.
Slave
SD (TXD) and RD (RXD): Negative logic
Slave



Connection to the RS-232C port of the master
A RS-232C/RS-485 communication converter is requited.
Slave
SG
T/R(B)
T/R(A)
RS-485
SG
T/R(A)
T/R(B)
RS-232C
Master
RS-232C/RS-485
converter
Shielded twisted
pair wire
Paired wire
Use a terminal resistor with a combined resistance of 100 :on the last controller.
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.

3. WIRING
IMCB14-E1 5



Connection with up to 31 slaves and one master
For all pertinent details on the RS-232C/RS-485 converter and junction branch box (BRA-
100B-2), see the respective instruction manuals.
Master
Master
RS-232C/RS-485 converter
BRA-100B-2
BRA-100B-2 BRA-100B-2
3029 311 2 3 4
SlavesSlavesSlaves
Slave address
example
RS-485
or
RS-232C
RS-485
RS-485

6IMCB14-E1
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 display mode Communication setting mode
Add -Slave address setting
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.
SET R/S
SV
PV
SET R/S
SV
PV
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ALM2ALM1AT OUT2OUT1

4. COMMUNICATION SETTINGS
IMCB14-E1 7
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
SV
PV
SV
PV
SV
PV
SV
PV
Input type and input range
display
Power On (Display for approx. 4 sec)
Display changes automatically
PV/SV display mode
Press and hold the SET key and press the
<R/S key at same time.
Slave address
(Add)
Communication speed
(bPS)
Data configuration
(bIT)
Interval time set value
(InT)
Press the
SET key.
Press and hold the
SET key and press
the <R/S key at
same time.
Press the SET key.
Press the SET key.
Press the
SET key.
Press the SET key.
Communication setting mode
SV setting mode
PV/SV display
mode

4. COMMUNICATION SETTINGS
IMCB14-E1
8
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 0and two-way communication is not
possible when the address is 0.
Symbol Name Setting range Description Factory set
value
Slave address 1 to 99* Set the controller slave
address.
0
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.
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

Setting procedure
Example: Setting the slave address to 15
1. Go to the communication setting mode so that slave address, Add, is displayed.
Slave address
SET R/S
SV
PV
ALM2ALM1AT OUT2OUT1

4. COMMUNICATION SETTINGS
IMCB14-E1 9
2. Press the UP key to enter 5at the first digit from the right.
3. Press the <R/S key to high-light the second digit from the right.
4. Press the UP key to enter 1at the second digit form the right.
5. Press the SET key to store the new slave address. The display automatically goes to the next
communication parameter, bPS.
SET R/S
SV
PV
ALM2ALM1AT OUT2OUT1
SET R/S
SV
PV
ALM2ALM1AT OUT2OUT1
R/S
SV
PV
SET
ALM2ALM1AT OUT2OUT1

4. COMMUNICATION SETTINGS
IMCB14-E1
10
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 Factory set
value
Communication
speed
0 : 2400 bps
1 : 4800 bps
2 : 9600 bps
Select the communication
speed
2
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.
Communication speed
SET R/S
SV
PV
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4. SETTING FOR COMMUNICATION
IMCB14-E1 11
2. Press the DOWN key to enter 1(4800 bps) at the first digit from the right.
3. Press the SET key to store the new communication speed. The display automatically goes to
the next communication parameter, bIT.
SET R/S
SV
PV
ALM2ALM1AT OUT2OUT1

4. SETTING FOR COMMUNICATION
IMCB14-E1
12
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 Factory set
value
Data
configuration
0, 6 or 7
See Data
Select data configuration
during communication
0
bIT Configuration
Table
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.
68 Even 1
78 Odd 1
Set the same data configuration 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 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.

4. SETTING FOR COMMUNICATION
IMCB14-E1 13



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.
Data configuration
2. Press the UP key to enter 6at the first digit from the right.
3. Press the SET key to store the new data configuration. The display automatically goes to the next
communication parameter, InT.
SET R/S
SV
PV
ALM2ALM1AT OUT2OUT1
SET R/S
SV
PV
ALM2ALM1AT OUT2OUT1

4. SETTING FOR COMMUNICATION
IMCB14-E1
14
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 Factory set
value
Interval time set
value
0 to 150* Set the value to set the interval
time
5
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 u1.666 ms
Interval time set value = Interval time y1.666 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.
1. Go to the communication setting mode so that slave address, Add, is displayed. Press the SET
key until the communication speed, InT, appears.
Interval time set value
SET R/S
SV
PV
ALM2ALM1AT OUT2OUT1