– 20 –
5
Chapter
Overview
The communication system with the MODBUS protocol always operates using a method where the master first sends a command
message and the applicable slave replys with a response message.
The following describes the communication steps.
● When the station number in the command message is the same as the unit’s station number
● When the station number in the command message is not the same as the unit’s station number
The master can communicate with an individual slave when multiple slaves are connected on the same circuit by the station
number specified in the master’s command message.
Master sends the command
message for the slave.
The slave checks whether the station
number in the received message is
the same as its own station number.
The slave runs the command and
sends a response message.
The slave throws out the received
message and waits for the next
command message. (No reply.)
When it’s the same When it’s not the same
Master Slave
Command Message
Response Message
Station number is the same
Master Slave
Command Message
Station number is not the same
To Next Page
Loading...
