Individual Functions
6
-
55
Message Format
In RS-422A/485 communications, the master sends commands to the slave and the slave responds. The mes-
sage format is configured for both sending and receiving as shown below and the length of data packets is
changed by the command (function) contents.
The space between messages must support the following:
Fig 6.40 Message Spacing
Slave Address
Set the Inverter address from 0 to 32. If you set 0, commands from the master will be broadcast (i.e., the
Inverter will not return responses).
Function Code
The function code specifies commands. There are three function codes, as shown below.
Data
Configure consecutive data by combining the storage register address (test code for a loopback address) and
the data the register contains. The data length changes depending on the command details.
Error Check
Errors are detected during communications using CRC-16. Perform calculations using the following method:
1. The factory setting for CRC-16 communications is usually 0, but when using the RS-422A/485 system, set
the factory setting to 1 (i.e., set all 16 bits to 1).
2. Calculate CRC-16 using MSB as slave address LSB and LSB as the MSB of the final data.
3. Also calculate CRC-16 for response messages from the slaves and compare them to the CRC-16 in the
response messages.
Slave address (1 byte)
Function code (1 byte)
Communications data
Error check (2 bytes)
Function Code
(Hexadecimal)
Function
Command Message
Response Message
Min.
(Bytes)
Max.
(Bytes)
Min.
(Bytes)
Max.
(Bytes)
03H
Read storage register contents
8
8
7
37
08H
Loopback test
8
8
8
8
10H
Write multiple storage registers
11
41
8
8
PLC to Inverter
Inverter to PLC
PLC to Inverter
Command message
Response message
Command message
Time (Seconds)
24 bits long
5 ms min.
H5-06
setting
24 bits long
