Отправлено albor 05 декабря 2002 г. 13:49 В ответ на: Вопрос по цоколевке RS485 отправлено albor 04 декабря 2002 г. 19:50

Actually, the definition of "A" or "B" for RS-485 interface doesn't
have any standard in EIA regulation. According to our study and survey,
almost all of 4-wire RS-485 devices define its "+"="B" & "-"="B".
Hence, we follow this common usage to design our pinouts.

However, we still find some RS-485 devices define their own pinouts.
I think it's still OK. No matter "+"="B" or "A", you just need to
follow a simple regulation to connect your RS-485 device. That is,

DTE ---------- device
Tx+ ----------> Rx+
Tx- ----------> Rx+
Rx+ <---------- Tx+
Rx- <---------- Tx-
SGND ---------- SGND

Then, everything will be fine.

Best Regards,

Tom Lu / Technical Support Engineer
Moxa Technologies Co., Ltd.