Hitachi EH-150 Series - Modbus Slave Mode; Overview

Chapter 6 Communication Mode
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Modbus Slave
6.4 Modbus slave mode
In modbus slave mode, EH-SIO responds to a query from master according to modbus protocol. Since operation from
receiving a query to sending a response is automatic, no other program is necessary than initial setting.
6.4.1 Overview
EH-SIO gets ready to receive a query after initial setting completed.
When EH-SIO receives a query from external device, EH-SIO analyzes the query and send a command to CPU
module. When EH-SIO receives a response from CPU module, EH-SIO converts the message to Modbus protocol
and send to the external device.
Figure 6.49 Overview of Modbus slave mode
 Supported function code
Supported function code and the meanings of EH-SIO are shown below.
Table 6.14 Supported function and meanings
Function
Function
Modbus Original
Corresponding Hitachi PLC I/O
01 (0x01)
Read Coil Status
Read continuous n points of bit output “Y”
02 (0x02)
Read Input Status
Read continuous n points of bit input “X”
03 (0x03)
Read Holding Registers
Read continuous n points of internal register “WR”
04 (0x04)
Read Input Registers
Read continuous n points of internal register “WM”
05 (0x05)
Force Single Coil
Write bit output “Y”
06 (0x06)
Preset Single Register
Write word internal output “WM”
Write word internal output “WR”
*
15 (0x0F)
Force Multiple Coils
Write continuous n point of bit output “Y”
16 (0x10)
Preset Multiple Registers
Write continuous n points of internal register “WR”
* Target internal output of function code 06 can be selected from “WM” and “WR” since software ver. 3.0 or newer.
Master
Command
Query
Response
No user program
Response