ABB AC500 PLC Hardware Manual page 1282

System Assembly, Construction and Connection
AC500 (Standard) > Connection and Wiring
1 Slave at the bus line end, bus termination with 120 Ω resistors
2 Master within the bus line, pull-up and pull-down activated
3 Slave within the bus line
4 Slave at the bus line end, bus termination with 120 Ω resistors
The cable shields must be earthed. See CS31 system bus
on page 1214.
2.6.4.8 CS31 System Bus
2.6.4.8.1 Connection of the Processor Module to the CS31 System Bus
COM1 of the The processor module can be used as a CS31 bus master. The connection is performed via the
Terminal Base serial interface COM1 used as a CS31 system bus.
1282
NOTICE!
If the bus is operated with several masters, the pull-up and pull-down resistors
may only be installed at one master.
The PM56xx processor mModule does not support the CS31 system bus.
3ADR010121, 13, en_US
Ä Chapter 2.5.4.4 "CS31 bus"
2019/04/17