Serial Interface Com2 - ABB Advant AC500 Manual

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.
Housing FE
1 FE
2 TxD
5 3 RxD/TxD-P
9
4 RTS
5 SGND
6 +5 V
6
1
7 RxD
8 RxD/TxD-N
9 CTS
COM2 9-pole, female
Figure: Pin assignment of the serial interface COM2
The following drawing shows an RS485 bus with the bus master at the line end.
0V
5
470
Ohms
8
120
3
Ohms
6
470
Ohms
6
+5V
Master at the
bus line end,
pull-up 470 Ohms
pull-down 470 Ohms
bus termination 120 Ohms
Figure: RS-485 bus, master at a line end
____________________________________________________________________________________________________________
V2
AC500 Hardware
Functional Earth
Functional Earth
RS-232
RS-485
RS-232
Signal Ground
RS-232
RS-485
RS-232
5
RxD/TxD-N
RxD/TxD-P
1
PE
Slave within
the bus line
Transmit Data output
Receive/Transmit positive
Request To Send output
0 V supply out
5 V supply out
Reiveive Data input
Receive/Transmit negative
Clear To Send input
Slave at the
bus line end,
bus termination
120 Ohms
1-40 System data
120
Ohms
AC500 / Issued: 05.2007