IAI America ROBO Cylinder Series - Manual (Page 24)

2. Specifications
16
Modbus
2.1 Communication Mode
In the Modbus protocol, communication takes place in a single-master/multiple-slave
configuration. In this communication, only the master (the PLC host in the example below)
issues a query to a specified slave (the RC controller connected to axis C in the example
below). When the specified slave receives this query, it executes the function specified in the
query, and then returns a response message (one communication cycle is completed with this
operation).
The query message format consists of the slave address (or broadcast), function code defining
the content of request, data, and error check.
The response message format consists of the function code confirming the content of request,
data, and error check. Following figure shows the query message format and response
message configuration.
Fig. 2.1
Query message
Device address (example: axis C)
Function code
Data
Error check
Response message
Data
Error check
Device address (example: axis C)
Confirmation function code
Axis A Axis B Axis C Axis D Axis E