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'RS232 vs RS422 vs RS485'
1998\09\29@084944 by Mark Birks

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Hi guys,

A quick serial question that I am still stumbling on :

I have a need to have a 9-pin port that can be EITHER RS232 (PC pinout) or
RS422/485 (pins 2,3,7,8) at any time.

The problems that I am encountering are the following :

1)      How to share the common pins (2,3,7,8) between the RS232 and
RS422/485 driver chips.
       Different voltage levels, impedances and all that.

2)      How to switch the termination for RS422/485 in and out (FETs ?)

I have seen these SIPEX chips but have heard bad things about their ESD
reliability etc.

Anyone know if tristatble RS232 and 422 chips can be tied together - are the
voltage ranges too different ?

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