YASKAWA VS-606V7 Series Instruction Manual page 115

(Example)
Reads out status signal, fault contents, data link status and frequency
reference from the VS-606V7 (slave 2).
Reference Message
Slave address
Function code
Upper
Start
number
Lower
Upper
Quantity
Lower
Upper
CRC-16
Lower
(For error code 03H, refer
to page 123.)
* Twice as much as the number of reference message.
• Example of Loop-back Test (08H)
Reference message is returned as a response message without being
changed. This function is used to check communication between the
master and the slave. Any arbitrary values can be used for test codes
or data.
(Example)
Reference Message
Slave address
Function code
Upper
Test
code
Lower
Upper
Data
Lower
Upper
CRC-16
Lower
114
Response Message
(at normal operation)
02H Slave address
03H Function code
00H Number of data*
20H First
holding
00H
register
04H Next
holding
45H
register
F0H Next
holding
register
Next
holding
register
CRC-16
Loop-back test of VS-606V7 (slave 1)
Response Message
(at normal operation)
01H Slave address
08H Function code
00H
Test
code
00H
A5H
Data
37H
DAH
CRC-16
8DH
02H
03H
08H
Upper 00H
Lower 65H
Upper 00H
Lower 00H
Upper 00H
Lower 00H
Upper 01H
Lower F4H
Upper AFH
Lower 82H
01H
08H
Upper 00H
Lower 00H
Upper A5H
Lower 37H
Upper DAH
Lower 8DH
Response Message
(at fault occurrence)
Slave address
Function code
Error code
Upper
CRC-16
Lower
Response Message
(at fault occurrence)
Slave address
Function code
Error code
Upper
CRC-16
Lower
02H
83H
03H
F1H
31H
01H
89H
01H
86H
50H