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3.13 Modbus-TCP/RTU
3.13.1 Introduction
Supported function codes are shown in the below table.
CPU EH-SIO
16# 10# Function code
Modbus-TCP Master
Modbus-RTU Master
Modbus-TCP Slave Modbus-RTU Master
0x01 01 Read Coils X - X
0x02 02 Read Discrete Inputs X - X
0x03 03 Read Holding Registers X X X
0x04 04 Read Input Registers X X X
0x05 05 Write Single Coil X - X
0x06 06 Write Single Register X X X
0x0F 15 Write Multiple Coils X - X
0x10 16 Write Multiple Registers X X X
0x17 23 Read/Write Multiple Registers X X X
X = Supported, - = Not supported
Modbus command processing is executed in bus cycle tack, which is configured in PLC settings of Device as below.
You can specify any existing IEC tasks. If the bus cycle task is <unspecified>, task with the shortest cycle time is
taken.
Note
If Modbus-RTU or TCP function is needed, be sure to use EHV-CPU1025 or higher model because Modbus libraries
require about 100KB of user program memory.
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