Modbus-Rtu Slave-Compatible Device Selection - Omron SYSMAC CS1W-SCB41-V1 Operation Manual

Modbus-RTU Slave Function for Replacing Existing PLCs
1:N Modbus-RTU Slave
1:1 Modbus-RTU Slave
9-6-2

Modbus-RTU Slave-compatible Device Selection

Pre-Ver. 1.2 Units
Note The differences between the command and response frames for 1:N Modbus-
RTU Slaves and 1:1 Modbus-RTU Slaves is as follows:
• Command Format
CS/CJ-series CPU Unit
I/O Memory
CIO Area 0
1
2
:
Work Area 0
1
2
:
Holding Area 0
1
2
:
DM Area 0
1
2
:
EM Area
0
1
DM Area settings are used to
2
allocate the area for each data
:
model except for discrete inputs.
• Response Format
@ 0 0 R D
Host Link Header
Unit No. code
The frame format for a 1:1 Modbus-RTU Slave is the same as that for the 1:N
Modbus-RTU Slave, except the @, Modbus-RTU Slave Unit No., and FCS are
omitted.
• Command Format
R D
Header code
• Response Format
R D 0 0
Header End code
code
In earlier models, when the host computer program used by the C-series
Modbus-RTU Slave Unit was reused in a CS/CJ-series PLC, data could not
be read normally for some programs due to the differences in Modbus-RTU
Slave specifications.
Modbus Data Models
Discrete Inputs
Coils
Input Registers
Holding Registers
× ×
0 0 * CR
Terminator
End FCS
code
* CR
Terminator
* CR
Terminator
Section 9-6
1
2
3
Modbus-RTU command
:
1
2
3
Modbus Commands
:
Read Coils
Read Discrete Inputs
1
Read Holding Registers
2
Read Input Registers
3
Write Single Coil
:
Write Single Register
Write Multiple Coils
1
Write Multiple Registers
2
3
:
299