SBC PCD2.M5 Series - Page 234

Hardware Manual for the PCD2.M5 Series│Document 26/856; Version EN 12│2014-07-24
Saia-Burgess Controls AG
Denitionsofserialinterfaces
Annex
A-3
A
A.2.2 RS-485/422
Signals to RS-485 (RS-422)
5V
2.5V
0V
4V
3V
2V
1V
VOH
VOL
VOZ
nicht aktiv
z.B. 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
In the idle state, RS-422isinthe“mark”position
RS-422:
Signal type Logical state Polarity
Data signal 0(space)
1(mark)
TXpositiveto/TX
/TXpositivetoTX
Control/message
signal
0(off)
1(on)
/RTS positive to RTS
RTS positive to /RTS
RS-485:
Signal type Logical state Polarity
Data signal 0(space)
1(mark)
RX-TXpositiveto/RX-/TX
/RX-/TXpositivetoRX-TX
Notallmanufacturersusethesameconnectionconguration,sothedatalinesmay
need to be crossed
To guarantee error-free operation of an RS-485 network, the network should be
terminated at both ends. Cable and line termination resistors should be selected in
accordance with manual 26/740 "Installation components for RS-485 networks".