ABB COMMANDER 500 - Electrical Installation; Host Computer Serial Communications; OPTO22 Boards for Use with Personal Computers; Two-Wire and Four-Wire Connection

3
2 ELECTRICAL INSTALLATION
This section describes the connection of serial data transmission cables between the master (host
computer) and slave COMMANDER 500 instruments on a MODBUS serial link. All connections other
than those used for serial communication are shown in Section 5 of the relevant User Guide .
2.1 Host Computer Serial Communications
An RS422/485 communications driver must be fitted to the host computer. It is strongly
recommended that the interface has galvanic isolation to protect the computer from lightning
damage and increase signal immunity to noise pick-up.
2.2 OPTO22 Boards for use with Personal Computers
Where a personal computer is used as the host computer, the following OPTO22 boards are
recommended for use with the COMMANDER 500 Series of instruments:
Part No. Computer Type
AC24 AT AT Bus IBM PC compatible
AC34 Microchannel IBM PC
2.3 Two-wire and Four-wire Connection – Figs. 2.1 and 2.2
MODBUS serial communications must be configured as either two-wire or four-wire serial links – see
Figs. 2.1 and 2.2. Two-/four-wire operation must also be selected in the Configuration Mode – see
Section 3.1.
Fig. 2.1 Pull-up and Pull-down Resistors (Two-wire Operation)
+5V
0V
1.8kΩ Pull-up
Resistor
1.8kΩ Pull-down
Resistor
Host Computer
Rx–
Rx+
Tx–
Tx+
'A'
'A
'B'
'B
GND
32
33
34
35
36
C500
Tx+/Rx+
Tx–/Rx–
Common