CAUTION!
Risk of communication faults!
When using inappropriate cables, malfunctions in communication may occur.
Only use network cables of the categories 5 (Cat 5, Cat 5e, Cat 6 or Cat 7) or
higher within PROFINET networks.
2.6.4.8 Modbus RTU connection details
The Modbus RTU protocol is implemented in the AC500 processor modules.
Modbus is a master-slave (client-server) protocol. The client sends a request to the server(s)
and receives the response(s).
Available serial interfaces can work as Modbus interfaces simultaneously.
The Modbus client operating mode of an interface is set with the function block
COM_MOD_MAST.
The Modbus operating mode and the interface parameters are set in the .
Table 205: Description of the Modbus protocol
Parameter Value
Supported standard See
Number of connection points 1 client
Max. 1 server with RS-232 interface
Max. 31 servers with RS-485
Protocol Modbus
Operating mode Client/server
Address Server only
Data transmission control CRC16
Data transmission speed From 9,600 bits/s to 115,200 bits/s
Encoding 1 start bit
8 data bits
1 or 2 stop bits
1 parity bit
)
Max. cable length for RS-485 on COM1 for
AC500 CPU
1.200 m at 19.200 baud
Point-to-point with RS-232 or bus topology with RS-485. Modbus is a master-slave protocol.
For further information on Modbus see chapter .
Technical data
Bus topology
System assembly, construction and connection
AC500 (Standard) > Connection and wiring
2022/01/313ADR010278, 3, en_US1000
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