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From: tell@oscar.cs.unc.edu (Stephen Tell)
Newsgroups: sci.electronics
Subject: Re: RS-232 powered modems
Summary: Minor nit: only the original Amiga had nonstd signals
Keywords: RS-232, Self-powered
Message-ID: <921@borg.cs.unc.edu>
Date: 27 Jan 91 20:12:03 GMT
References: <2820@casbah.acns.nwu.edu> <1991Jan21.050956.26328@athena.cs.uga.edu> <1991Jan21.142804.5726@uhura.neoucom.EDU>
Sender: news@cs.unc.edu
Organization: University of North Carolina, Chapel Hill
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In article <1991Jan21.142804.5726@uhura.neoucom.EDU> wtm@uhura.neoucom.EDU (Bill Mayhew) writes:
>
>>>On the other hand however, the RS-232 standard has connectors for +5V on
>>>its line. 
>>
>>Er... not as far as I can determine. I've never seen one that did.
>
>There are a few non-standard computers that supply power on their
>COM ports, the Amiga series from Commodore, for example.  In fact
>the Amiga is a bit of a problem because there is enough oomph on
>the COM port to toast improperly wired items, though normal modems
>usually have Commodore's pin uncommited.

Just a minor correction:  This was true of the original Amiga-1000, but
not of the whole series.  The Amiga-2000 has a nice, well-behaved serial
port that is electricaly very similar to the one on PCs and other machines.
I believe this is true of the 500 and 3000 machines as well.

The 1000 did have all sorts of weird signals on pins that were unused on
"standard" RS232.  These signals are available on some sort of auxiliary
pin header inside the 2000, so an adaptor is available to create a port
that looks like the one on the 1000.  I think there were problems with the
nonstandard signals, so thats why they changed on the later models.

Incidently, the parallel port was also revised so that the later models can
use standard IBM-PC printer cables, while the A1000 could not.

--------------------------------------------------------------------
Steve Tell       tell@.cs.unc.edu      919 968 1792     #5L Estes Park apts
CS Grad Student, UNC Chapel Hill.                       Carrboro NC 27510