Saia-Burgess Controls AG
Hardware manual for PCD3 series │ Document 26-789 ENG19│ 2018-06-29
Appendix
A
A-4
Denitionsfortheserialinterfaces
A.2.2 RS-485/422
Signals to RS-485 (RS-422)
5V
2.5V
0V
4V
3V
2V
1V
VOH
VOL
VOZ
not active
e.g. Startbit
/TX
TX
mark space
= mark
VOZ = 0.9 V min. … 1.7 V
VOH = 2 V min. (with load) … 5 V max. (without load)
VOL = –2 V … -5 V
RS-422 is in active condition in mark position
RS-422
Signal type Logical status Polarity
Data signal 0 (space)
1 (mark)
TX positive for /TX
/TX positive for TX
Control/
message signal
0(o)
1 (on)
/RTS positive for RTS
RTS positive for /RTS
RS-485
Signal type Logical status Polarity
Data signal 0 (space)
1 (mark)
RX-TX positive for /RX-/TX
/RX-/TX positive for RX-TX
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