YASKAWA E7LVD002 Technical Manual page 261

Loopback Test (08H)
The loopback test returns the command message directly as the response message without changing the contents to check the
communications between the master and slave. Set user-defined test code and data values.
The following table shows a message example when performing a loopback test with the slave 1 Drive.
Command Message
Slave address
Function code
Higher
Test Code
Lower
Higher
Data
Lower
Higher
CRC-16
Lower
Write In Several Holding Registers (10H)
Write the specified data to the registers from the specified addresses. The written data must be consecutive, starting from the
specified address in the command message: Higher 8 bits, then lower 8 bits, in storage register address order.
The following table shows an example of a message when a forward run command has been set at a speed command of
60.0 Hz in the slave 1 Drive by the PLC.
Command Message
Slave Address
Function Code
Higher
Start
Address
Lower
Higher
Quantity
Lower
No. of data
Higher
Lead data
Lower
Higher
Next data
Lower
Higher
CRC-16
Lower
Set the number of data specified using command messages as quantity of specified messages x 2. Handle
IMPORTANT
response messages in the same way.
Response Message
(During Normal Operation)
01H Slave address
08H Function code
00H
Test Code
00H
A5H
Data
37H
DAH
CRC-16
8DH
Fig. D.8 Function Code 08H Message Example
Response Message
(During Normal Operation)
01H Slave Address
10H Function Code
00H
Start
Address
01H
00H
Quantity
02H
04H
CRC-16
00H
01H
02H
58H
63H
39H
Fig. D.9 Function Code 10H Message Example
Communications D - 9
01H
08H
Higher 00H
Lower 00H
Higher A5H
Lower 37H
Higher DAH
Lower 8DH
01H
10H
Higher 00H
Lower 01H
Higher 00H
Lower 02H
Higher 10H
Lower 08H
* No. of data = 2 x (quantity)
Response Message
(During Error)
Slave address 01H
Function code 89H
Error Code 01H
Higher 86H
CRC-16
Lower 50H
Response Message
(During Error)
Slave Address 01H
Function Code 90H
Error code 02H
Higher CDH
CRC-16
Lower C1H