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From: palmer@tybalt.caltech.edu (David Palmer)
Newsgroups: comp.sys.mac
Subject: Mac Serial ports
Message-ID: <12742@cit-vax.Caltech.Edu>
Date: 21 Nov 89 01:12:29 GMT
Sender: news@cit-vax.Caltech.Edu
Reply-To: palmer@tybalt.caltech.edu.UUCP (David Palmer)
Organization: California Institute of Technology
Lines: 22

I am wiring up a micro-controller (an (oh the shame of it) Intel 8052
with a built-in (double shame) BASIC interpreter)

This controller has a TTL (0 - 5V) input-output serial port.  What do
I need to do to get my Mac to speak to it?  I am wiring my own cable.
Do I have to wire the RxD- line on the Mac to set it to +2.5 V so that
the differential goes positive and negative? or does it drift to that
value automatically?

Also, the controller serial port is set up to use an inverting buffer.
Is it reasonable to just use the RxD- and TxD- lines from the Mac, and
wire the RxD+ line to +2.5V?  This would eliminate another chip from
what is now a 4-chip design, which is aesthetically pleasing even if
it is bad engineering practice.

Thanks in advance.

		David Palmer
		palmer@tybalt.caltech.edu
		...rutgers!cit-vax!tybalt.caltech.edu!palmer
	Meanwhile, on eng.string.floss, the waxed vs. unwaxed flamewar
	continues unabated.