ABB AC500 PLC Hardware Manual page 1293

Station 1
Bus segment 1:
max. 31 stations
+ 1 repeater
Fig. 243: Principle example for a PROFIBUS-DP system with repeaters (1500 kbit/s baud rate)
2.6.4.12 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.
Technical data
The Modbus operating mode and the interface parameters are set in the PLC configuration.
Description of the Modbus protocol:
Supported standard
Number of connection points
Protocol
Operating mode
Address
Data transmission control
Data transmission speed
Encoding
Max. cable length for RS-485
If a Processor Module provides more than one serial interface, both interfaces (COM1/COM2)
can be operated simultaneously as Modbus interfaces and can operate as Modbus server as
well as Modbus client.
2019/04/17
max. 200 m
Repeater
R
Station 31
3ADR010121, 13, en_US
System Assembly, Construction and Connection
AC500 (Standard) > Connection and Wiring
max. 200 m
R
Station 32 Station 61
Bus segment 2:
max. 30 stations
+ 2 repeaters
PM55x and PM56x: EIA RS-485
PM57x, PM58x and PM59x: EIA RS-232 /
RS-485
1 client
Max. 1 server with RS-232 interface
Max. 31 servers with RS-485
Modbus
Client/server
Server only
CRC16
Up to 187.500 baud
1 start bit
8 data bits
1 parity bit, (optional) even, odd, mark or
space
1 or 2 stop bits
1.200 m at 19.200 baud
Repeater
R R
1293