ABB Advant AC500 - Serial Interface COM2

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V2 AC500 Hardware 1-40 System data AC500 / Issued: 05.2007
Serial interface COM2 of the CPU Terminal Bases
The serial interface COM2 is connected via a 9-pole SUB-D plug. It is configurable for RS-232 or RS-
485 and can be used for
• an online access (RS-232 programming interface for PC/Control Builder)
• a free protocol (communication via the COMSND and COMREC function blocks)
• Modbus RTU, master and slave
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:
• two resistors of 120 Ohms each at both line ends (to avoid signal reflections)
• in addition, a pull-up resistor at RxD/TxD-P and a pull-down resistor at RxD/TxD-N. These two
resistors care for a defined high level on the bus, while there is no data exchange.
It is useful, to activate both the pull-up and the pull-down resistors, which only are necessary once on
every bus line, at the bus master.
COM2 9-pole, female
1
2
3
4
5
6
7
8
9
FE
TxD
RxD/TxD-P
RTS
SGND
+5 V
RxD
CTS
1
5
9
6
Functional Earth
RS-232
RS-485
Request To Send
Signal Ground
Reiveive Data
Clear To Send
Housing Functional Earth
Transmit Data
output
Receive/Transmit positive
RS-232 output
RS-232 input
RS-485 Receive/Transmit negative
RS-232 input
0 V supply out
5 V supply out
RxD/TxD-N
FE
Figure: Pin assignment of the serial interface COM2
The following drawing shows an RS485 bus with the bus master at the line end.
5
6
3
6
8
5
1
RxD/TxD-P
RxD/TxD-N
0V
+5V
120
Ohms
470
Ohms
470
Ohms
Master at the
bus line end,
pull-up 470 Ohms
pull-down 470 Ohms
bus termination 120 Ohms
PE
Slave within
the bus line
Slave at the
bus line end,
bus termination
120 Ohms
120
Ohms
Figure: RS-485 bus, master at a line end