C.7 Message Format
C.7 Message Format
♦ Message Content
In MEMOBUS/Modbus communications, the master sends commands to the slave, and the slave responds. The message
format is configured for both sending and receiving as shown below, and the length of data packets depends on the
command (function) content.
♦ Slave Address
The slave address in the message defines the note the message is sent to. Use addresses between 0 and FF (hex). If a
message with slave address 0 is sent (broadcast), the command from the master will be received by all slaves. The slaves
do not provide a response to a broadcast type message.
♦ Function Code
The three types of function codes are shown in the table below.
Function
Code
Data Length (bytes)
Function Name
Command Message
Response Message
Minimum
Maximum
Minimum
Maximum
03H
Read MEM OBUS/M odbus registers
8
8
7
37
08H
Loopback test
8
8
8
8
10H
Write to m ultiple MEM OBUS/M odbus registers
11
41
8
8
♦ Data
Configure consecutive data by combining the MEMOBUS/Modbus register address (test code in case o f a loopback test)
and the data the register contains. The data length changes depending on the command details.
A drive MEMOBUS/Modbus register always has a data length of two bytes. Therefore data written into drive registers
must also always have a length o f two bytes. Register data read out from the drive will always consist o f two bytes.
YASKAWA ELECTRIC SIEP C710616 33D YASKAWA AC Drive L1000A Technical Manual
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