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From: gpatrick@handel.mpr.ca (Greg Patrick)
Newsgroups: comp.sys.amiga.hardware
Subject: Oh please help!  Serial port/Modem prob.
Message-ID: <2358@kiwi.mpr.ca>
Date: 28 Sep 90 15:24:47 GMT
Sender: news@eric.mpr.ca
Lines: 31

Does anyone know much about the serial port on the Amiga 500?

I have the following (damn annoying!) problem:

I have a Smart One 2400 baud modem that works just dandy with my former
roomie's PC clone.  If I plug the modem into the wall and turn it on,
without connecting it to my Amiga, everything is fine - only the MR
(modem ready) light comes on.

However, if I connect the modem to my Amiga and turn them both on, then
the modem has the MR, the SD (send data), and the TR (terminal ready - I
don't really know what this one signifies) lights all come on.  I've
tried 2 cables, one brand new, so I doubt it's that.  I know the modem
works with a PC so it's not the modem.

I think either I have shorted pins on my Amiga serial port or that one
or both of my 8520 chips are bad.  My Amiga manual lists the pinouts for
the serial port but doesn't give the active voltage levels, nor does it
tell what voltage each pin should be if the port is not being used.

What do you think it is?
Also, is an 8520 chip a standard chip that I can pick up at an
electronics shop, or is it a Commodore chip that I can't easily get?

Please reply to:  gpatrick@mprgate.ca or (if that bounces) 
gpatric@handel.mpr.ca

P.S.  I'm desperate!  I need to log on to work from home!
P.P.S.  I'm kind of a novice Amiga guy, so try to be detailed. 

Greg.