Controlling The Rs 422 Receiver; Terminators And Open-Circuit Potential For Rs 422; Fig. 8-4: Enabling The Rs 422 Transmitter - Addi-Data ADDICOM PA 7400 Series Technical Description

PA 7400
•
Make sure that the values of data bits D1-D7 are not overwritten when writing
in the MODEM CONTROL REGISTER A(B) on Base-S1(2) +4.

Controlling the RS 422 receiver

You control the RS 422 receiving component with bit RD-EN-1(2).
•
Set jumper J16(7) on pos. B.
Bit RD-EN-1(2) is the bit D1(3) of address Base-S1 +7 of the DUART
component.
RD-EN-1(2) = 0
RD-EN-1(2) = 1

Terminators and open-circuit potential for RS 422

The receive lines RxA+(RxB+) and RxA-(RxB-) are in RS 422 at an open-
circuit potential through 1 K ohm resistors.
If the board is located at the end of the network
•
insert a terminator through jumper J18(13).
J18(13) in pos. A
J18(13) in pos. B
IMPORTANT!
If the board does not receive data, and if you want to detect whether a
line interruption has occurred (damaged line, no device connected),
•
invert the open-circuit potential of the receive lines RxA+(RxB+) and RxA-
(RxB-).
Set the jumpers as follows:
J19(14) in pos. A
J20(15) in pos. B
36

Fig. 8-4: Enabling the RS 422 transmitter

Reception is possible (reset value)
Reception is not possible
120 Ω terminator
100 Ω terminator
Technical description Chapter 8