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Path: utzoo!linus!philabs!cmcl2!seismo!mcvax!unido!vr0z05
From: vr0z05@unido.UUCP
Newsgroups: net.micro.pc
Subject: Need help with AT RS-232!!!
Message-ID: <10000013@unido.UUCP>
Date: Wed, 7-Aug-85 22:06:00 EDT
Article-I.D.: unido.10000013
Posted: Wed Aug  7 22:06:00 1985
Date-Received: Sun, 11-Aug-85 03:32:33 EDT
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Nf-ID: #N:unido:10000013:000:1677
Nf-From: unido!vr0z05    Aug  8 00:06:00 1985


[This line for the old byte eater]

I need help with AT-02!!!

Hooray,

it took 9 months to get our baby (the AT-02), but now we're very happy
and proud parents. But there still remain some questions.

Our authorized IBM-Dealer is not able to sell us the Technical Reference
Manual for the AT. He says that he hasn't got any form Big Blue. But I
have to adapt a selfmade communications program from our former XT to the
AT. Thinking that the AT is upward compatible I tried to put my
communications cable into the AT, but !!! STOP !!! the old Canon DB-25
is replaced by a Canon DB-9 plug. What now? We have no circuit diagram
how the DB-9 plug is configured. Is anybody out there in net-land able
to send me this configuration plan by E-mail???

Also I have realized that the programming of the RS-232 interface must
be a little bit different to the former XT. But I couldn't find out
what has changed. A testprogram which shortens input and output of the
RS-232 via the Modem Control Register (Bit 4 in $3FC set) and that ran
correct on the XT doesn't do anything on the AT. I can send a character,
I'm able to receive him via polling, the 8250 (is it really a 8250???)
produces an interrupt ($04 in $3FA), but the processor never receives the
interrupt, though I have set Bit 3 in the Modem Control Register (for OUT2)
and Bit 4 on Port $21 (the 8259, again: is there a 8259 in the AT???) in 
order to allow interrupts. What is wrong.

				   Please help!!!
				   Many thanks in advance.


     Uwe Hoch
     Computer Science Department, University of Dortmund
     4600 Dortmund 50, P.O. Box 500500, W.-Germany
     E-mail address UUCP: ...ihnp4!hpfcla!hpbbn!unido!vr0z05