ABB AC500 PLC Hardware Manual page 97

Bus line
Remarks
Cable Lengths
The maximum possible cable length of a serial connection subnet within a segment depends on
the baud rate (transmission rate).
COM1 - RCOM:
Baud rate
2.4 kBaud to 19.2 kBaud
COM2 - CONSOLE:
Baud rate
19.2 kBaud
Bus Termination (RS-485 only)
The line ends of the bus segment must be equipped with bus termination resistors. Normally,
these resistors are integrated in the interface connectors.
120
Ohms
Master at the bus line end,
pull-up and pull-down activated,
bus termination 120 Ohms
1.3.2.3 State LEDs
LED
2019/04/17
Communication Modules (AC500 Standard) > CM574-RCOM for RCOM/RCOM+
1 1
2 2
3 3
4 4
Slave within
the bus line
Color
PWR Green
RDY Yellow
RUN Green
3ADR010121, 13, en_US
Commonly used telephone cables with PE insulation and a
core diameter of > 0.8 mm are usually sufficient.
Cables with PVC core insulation and core diameter of
0.8 mm can be used up to a length of approx. 250 m. In this
case, the bus terminating resistor is approx. 100 Ω.
Maximum cable length
On request
Maximum cable length
On request
1
2
3
4
Slave at the bus line end,
bus termination 120 Ohms
State Description
ON Voltage is present
OFF Voltage is missing
ON Communication module is ready
Flashes Event queue blocked (slave devices only)
cyclically
OFF Hardware defective
ON Normal operation
Device Specifications
Term. P
120 RxD/TxD-P
Ohms RxD/TxD-N
Term. N
97