Path: utzoo!attcan!utgpu!jarvis.csri.toronto.edu!mailrus!tut.cis.ohio-state.edu!pt.cs.cmu.edu!rochester!ken
From: ken@cs.rochester.edu (Ken Yap)
Newsgroups: comp.os.minix
Subject: Re: 75/1200 baud modem in software?
Message-ID: <1989Aug26.145338.20772@cs.rochester.edu>
Date: 26 Aug 89 14:53:38 GMT
References: <539@vice2utc.chalmers.se> <1052@kuling.UUCP> <431@tardis.Tymnet.COM> <431@xdos.UUCP>
Reply-To: ken@cs.rochester.edu.UUCP (Ken Yap)
Organization: U of Rochester, CS Dept, Rochester, NY
Lines: 16

|>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.
|
|I would think there's a chance that they wouldn't screw it up, since
|we're basically talking about what would look like a glitch in 1/16th
|of the received waveform. Would depend on how the receiver hardware was
|designed, wouldn't it? Might still be worth a try.
|	Doug

It depends on the hardware. Most UARTs sample in the middle of the
bit period, the middle being determined by counting off half
of the divide count, e.g. 8 clock pulses in divide by 16 mode.
If your glitch happens at the wrong time...