Loop-Back Test [08H] - Hitachi WJ Series User Manual

Chapter 11
11.2.5

Loop-back Test [08h]

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