Instruction Manual

Section 3: Installing the Instrument and Plug-In Cards
10/08 28 51207 Revision 1
PR 5510/04 RS-422/485
When mounting, the RS-485/422 interface must be configured by DIL switch S101 on the card.
Using RS-485 is compulsory with a multi-point connection (tristate status). The RS-485 interface
can be used also for point-to-point connection. Like 2-wire or 4-wire connections, this is dependent
on the other communicating units.
A 2-wire connection is half-duplex and cannot send and receive simultaneously. It requires
corresponding driver programming (see relevant instrument manual).
Factory setting Switch S101 Settings for RS-422/ 485
1: Tristate enable: OFF – RS-422 ON – RS-485
2: Rx enable OFF – 4-wire ON – 2-wire
3: Rx pull-up resistor: OFF – not connected ON - (RxB 1k54 +V)
4: Rx bus termination: OFF – not connected ON - (RxA 205E
RxB)
5: Rx pull-down resistor: OFF – not connected ON - (RxA 1k54 -V)
Overview of which switches must be closed (ON) for which mode:
Two-wire system Four-wire system
S101
Point to point Bus Point to point Bus
Master RS-485
1, 2, 3, 4, 5 =
on
RS-485
1, 2, 3, 4, 5 = on
RS-422
4 = on
RS-422
3, 4, 5 = on
Individual slave RS-485
1, 2 = on
- RS-422
4 = on
-
Other slaves - RS-485
1, 2 = on
- RS-485
1 = on (default)
Last slave - RS-485
1, 2, 3, 4, 5 = on
- RS-485
1, 3, 4, 5 = on