Hitachi WJ C1 Series

Chapter 11 RS485 Communication
11-2-7
11.2.5 Loop-back Test [08h]
 How to check whether devices can be sent and received on Modbus communication normally?
 Used to check communication between master and slave. The test data can be any value.
 An example of a loopback test to an inverter with slave address 1 is shown below.
Query
No.
Field name
Example
(HEX)
1
Slave address
*1
01
2
Function code
08
3
Test subcode (High)
00
4
Test subcode (Low)
00
5
Data (High)
Any value
6
Data (Low)
Any value
7
CRC-16 (High)
CRC
8
CRC-16 (Low)
CRC
Response
No.
Field name
Example
(HEX)
1
Slave address
*1
01
2
Function code
08
3
Test subcode (High)
00
4
Test subcode (Low)
00
5
Data (High)
Any value
6
Data (Low)
Any value
7
CRC-16 (High)
CRC
8
CRC-16 (Low)
CRC
*1. For broadcast, there is no response.
 The test subcode only supports echoing query data (00h, 00h). Other commands are not
supported.
A
!
Q