A
A-4  CP1L Programming Examples
SYSMAC CP1L Getting Started Guide 143
Appendix
A-4-7 Using Inverters for Speed Control (1) 
 Functions Used
zModbus-RTU Easy Master Function
By using Modbus-RTU easy master function, Modbus-compliant slave devices (i.e. 
inverters) can be controlled easily via serial communication. 
To perform serial communication on CP1L, install an optional serial communication 
board (RS232C or RS422A/485). 14/20-point I/O units can have 1 optional serial 
communication board installed. 30/40-point I/O units can have up to 2 boards 
installed. 
The Modbus-RTU easy master function allows for easy communication with 
components connected via a serial connection board. 
In the DM fixed allocation words for Modbus-RTU easy master, allocate the slave 
address, function, and data to the Modbus slave device. After the allocations have 
been made, Modbus-RTU commands can be sent by turning the software switch ON. 
Received responses are automatically stored in the DM fixed allocation words. 
Note Modbus-RTU easy master execution bits and DM Fixed Allocation words depend 
on unit type, 14/20-point I/O units or 30/40-point I/O units. For details, refer to CP 
Series CP1L CPU Unit User's Manual (W462).
COMM
COMM
Option 
board slot
CP1L
RS-232C 
option board 
CP1W-CIF01
RS-422A/485 
option board
CP1W-CIF11
Modbus-RTU easy master function 
execution switch A640 CH bit 00 
(for port 1)
Describe Modbus-RTU commands in the 
DM fixed allocation words. 
Communication can then be enabled by 
simply turning ON the software switch 
A640 CH bit 00. 
Slave address
FUNCTION code
Communication data
Communication data bytes
D32300
D32301
D32302
D32303
15 08 07 00
Modbus-RTU
OMRON inverter 
CIMR-V7 / CIMR-F7
CP1L
Slave address
FUNCTION code
Communication data
Slave address
FUNCTION code
Communication data
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