Serial floppy drives

From: Dwight K. Elvey <dwightk.elvey_at_amd.com>
Date: Wed Sep 4 20:04:00 2002

>From: tlindner_at_ix.netcom.com
>
>> On Wed, 4 Sep 2002, Tony Duell wrote:
>> > However, the original question mentioned RS232. Which is _not_ the same
>> > as serial. RS232 implies certain voltage levels.
>> > The CBM and Atari drives do not use an RS232 interface.
>>
>> AND,..
>> If I recall correctly, the Tandy Pdd1, although it was "almost
>> RS-232" used TTL, NOT RS-232 voltage levels. There were some trivial
>> adapters available to permit it to work with "real" RS-232 signals.
>
>I always thought that was called RS-422.
>
>The Macintosh standard serial port was a RS-422 serial port. When I went
>to look up what that meant, the only difference I could find was the
>voltage levels.
>
>RS-422: 0v to 5v
>RS-232: -5v to 5v
>
>The documentation I found went on to say that RS-422 was backaward
>compatiable with RS-232.
>
>--
>tim lindner tlindner_at_ix.netcom.com
>


Hi
 No, 422 is not backwards compatible with 232.
RS-422 and RS-485 are both specs for driving differential
lines. RS-232 can be +/- 12 volts but the receiver may
have lower levels ( I forgot what the requirement was ).
 The document was not correct about RS-232/RS-422. It may
be that one could make them work under specific conditions
but these signals are not backward compatible.
Dwight
Received on Wed Sep 04 2002 - 20:04:00 BST