YASKAWA E7LVD002 Technical Manual page 258

Message Format
In Modbus communication, the master sends commands to the slave, and the slave responds. The message format is
configured for both sending and receiving as shown below. The length of the data packets is changed by the command
(function) contents.
The space between messages must support the following:
Slave Address
Set the Drive address from 0 to 32. If 0 is selected, commands from the master will be broadcast (i.e., the Drive will not return
responses).
Function Code
The function code specifies commands. There are four function codes, as shown below.
Function Code
(Hexadecimal)
03H
06H
08H
10H
* Minimum bytes for a normal Response Message (error response message is always 5 bytes).
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.
DDC to Drive
Command message
24 bits long
Table D.3 Modbus Function Codes
Function
Reading/Holding Register Contents
Write In Single Holding Register
Loopback Test
Write In Several Holding Registers
Slave address
Function code
Data
Error check
Fig. D.4 Message Format
Drive to DDC
Response message
H5-06
24 bits long
setting
Fig. D.5 Message Spacing
Command Message
Min.
(Bytes)
8
8
8
11
Communications D - 6
DDC to Drive
Command message
Time (Seconds)
5 ms min.
Response Message
Max. Min.*
(Bytes) (Bytes)
8 7
8 8
8 8
41 8
Max.
(Bytes)
37
8
8
8