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From: dgold@apple.UUCP (David Goldsmith)
Newsgroups: net.micro.mac
Subject: Re: Serial Port
Message-ID: <273@apple.UUCP>
Date: Wed, 5-Nov-86 19:48:59 EST
Article-I.D.: apple.273
Posted: Wed Nov  5 19:48:59 1986
Date-Received: Thu, 6-Nov-86 20:52:28 EST
References: <378@uwmacc.UUCP> <7126@boring.mcvax.UUCP> <1120@cit-vax.Caltech.Edu>
Reply-To: dgold@apple.UUCP (David Goldsmith)
Distribution: net
Organization: Apple Computer Inc., Cupertino, USA
Lines: 32

In article <1120@cit-vax.Caltech.Edu> palmer@cit-vax.UUCP (David Palmer) writes:
>...
>I would like to use the serial port with an external clock for some hardware
>I am making...
>The serial driver section in my copy of Inside Macintosh (Phone book version)
>does not tell me how to use the external clock, nor does it tell me how
>to change the clocking frequency from whatever it usually is (16 times
>the baud rate, I think) to equal the baud rate.
The serial driver only supports asynchronous communications at one of a fixed
set of baud rates.  In order to communicate at 400KB, you will need to use
one of the synchronous communication modes of the Z8530 SCC hardware in the
Mac (documented in the hardware chapter).  You will have to write your own
driver software to accomplish this, and access the hardware directly.
In addition to Inside Mac, you will need the Z8530 technical reference,
available from the manufacturer.

Although the Z8530 supports a large number of communications modes
(async, bisync, HDLC, SDLC, etc), the serial driver was only intended
to support standard async, not any of the fancier stuff.  I'm not sure
the Z8530 even supports async above 56KB.  AppleTalk uses one of the
synchronous modes and has its own low-level device driver.



-- 
David Goldsmith
Apple Computer, Inc.
MacApp Group

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