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From: jms@tardis.Tymnet.COM (Joe Smith)
Newsgroups: comp.os.minix,comp.sys.amiga,comp.sys.amiga.tech
Subject: Re: 75/1200 baud modem in software?
Summary: Start and Stop bits get in the way.
Message-ID: <431@tardis.Tymnet.COM>
Date: 18 Jul 89 03:28:38 GMT
References: <539@vice2utc.chalmers.se> <1052@kuling.UUCP>
Reply-To: jms@tardis.Tymnet.COM (Joe Smith)
Organization: McDonnell Douglas Field Service Co, San Jose CA
Lines: 17

In article <1052@kuling.UUCP> marten@kuling.UUCP (M}rten Norman) writes:
>As 1200/75=16 it _should_ be possible, if you are willing to fiddle with the
>hardware registers. Just send 16 "1200-speed-bits" to represent a "75-bit".
>The Hardware serial output register should agree with this, but i _dont_
>think it's supported in standard software :-)

When you send 8 bits to an async line, the hardware sends 10 bits by
adding a start bit and a stop bit.  Although one byte at 75 baud takes
the same amount of time to transmit as 16 bytes at 1200 baud (160 bit times
total), you can only specify 128 of the 160 bits.  The remaining 32 bits
will screw up the receiver at the far end.

-- 
Joe Smith (408)922-6220 | SMTP: JMS@F74.TYMNET.COM or jms@tymix.tymnet.com
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