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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.
N o t e
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.