Specifications

58
Schneider Electric
The Modbus Protocol (continued)
Description of exchanges
Broadcast commands are always write commands. Slaves do not answer such
commands.
Exchanges take place at the initiative of the
master. They include a query from the
master and a response from the slave.
E52348
Master
Slave 1
Slave 2 Slave 3
Query
Response
E52349
All frames exchanged have the same
structure.
Queries from the master are addressed
either:
b To a specific slave (identified by its
number in the first byte of the query frame.
b To all slaves (broadcasting).
CRC 16
Function
code
Data
zone
Control
zone
Slave n°
E52350
Master
Broadcast
Slave 1
Slave 2 Slave 3
Guide to Integration
Modbus / Jbus