NOTICE!
Risk of malfunctions!
The pull-up resistors must be used only one time within a bus line.
Use the pull-up resistors only at 1 master.
The cable shields must be earthed. See CS31 system bus
Ä
Chapter 2.5.4.4 “CS31 bus”
on page 1214.
2.5.4.3 Serial Interface COM2
The serial interfaces COM1 and COM2 are designed according to the standard EIA RS-485.
Both interfaces can be operated in RS-485 mode.
Parameter Value
Standard of the serial interfaces RS-485
Interface connectors COM1: 9-pin D-sub connector (female)
COM2: 5-pole connector with screw-type con-
nection (optional)
Electrical isolation none
Serial interface parameters Configurable by the software
Operating modes Programming or data exchange
Supported protocols Modbus or serial data exchange using special
software function blocks
The serial interface COM2 is connected via a 5-pole terminal block and can be used for
● online access
● free protocol communication
● Modbus RTU, client and server
The serial RS-485 Interface is not electrically isolated.
It is not intended to use COM2 to establish a CS31 system bus.
If the RS-485 bus is used, each interconnected bus line (each bus segment) must be electrically
terminated. The following is necessary:
● 2 resistors of 120 Ω each at both line ends (to avoid signal reflections)
● A pull-up resistor at RxD/TxD-P and a pull-down resistor at RxD/TxD-N. These 2 resistors
care for a defined high level on the bus, while there is no data exchange.
System Assembly, Construction and Connection
AC500-eCo > Connection and Wiring
2019/04/173ADR010121, 13, en_US1212
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