Hardware manual PCD1.M2220-C15 │ Document 27-640 – Version ENG03 │ 2020-03-25
Saia-Burgess Controls AG
Definition of serial interfaces
Appendix
A-2
A
A.2
Definition of serial interfaces
A.2.1 RS-485
Signals to RS-485
VOH
VOL
5 V
2.5 V
0 V
4 V
3 V
2 V
1 V
VOZ
/TX
TX
not active
e.g. start bit
mark
space
VOZ = 0.9V min.
VOH = 1.5V min. (with load) … 3.6V max. (without load)
VOL = –1.5V min. (with load) … –3.6V max. (without load)
Signal type
Logical status
Polarity
Data signal
0 (empty)
1 (character)
RX-TX positive on /RX-/TX
/RX-/TX positive on RX-TX
Not all manufacturers use the same connection configuration, so users may have to cross the data lines
To guarantee an error-free operation of a RS-485 network, the network should be terminated at both
ends. Cables and terminating resistors should be selected in accordance with the manual 26-740
“Installation components for RS-485 networks”.
