Path: utzoo!attcan!uunet!ginosko!usc!ucsd!ucbvax!HASARA5.BITNET!ROBBEL%NKIVXH.SURFNET
From: ROBBEL%NKIVXH.SURFNET@HASARA5.BITNET
Newsgroups: comp.sys.apple
Subject: Apple 2e doesn't see my 6522's !!
Message-ID: <8909060935.aa25446@SMOKE.BRL.MIL>
Date: 6 Sep 89 14:10:00 GMT
Sender: daemon@ucbvax.BERKELEY.EDU
Organization: The Internet
Lines: 32

Hi,

I'm having this trouble with a parallel interface I'm building for my //e. I
have some experience building things (MIDI-interface, RS-232, sound, you know)
and have never had any trouble. Now I'm working on a card consisting of 2 VIA's
(6522) and I just can't get it to work !!

The design is pretty straightforward:

        2 VIA's and one 74LS138 3-to-8-decoder for address-decoding:

        A4 - A5 - A6 connected to input lines,
        A7 to first enable (active low),
        _________
        IO-SELECT to second enable (active low),
        third enable to +5V (active high).
        Output 1 of the LS138 is connected to VIA-1, output 2 to VIA-2.

        A0 to A3 are connected to R(-egister)S(-elect)0 to RS3 of both VIA's.
        As a clock I'm just using Phi-0 (I also tried inverted Phi-1 but that
        didn't work either). No patching done to the clock.

The interface should be in the address range $C700 to $C7FF (if I put it in
slot 7; VIA 1 : $C700-$C70F,  VIA 2: $C710-$C71F) but there's nothing there !!

Is there something I don't know about and is causing me this trouble ? Have I
overlooked something?? Could someone shed some light onto this subject ???
Any help is _very_ appreciated ... thanks in advance.

Robert Belleman,        ROBBEL%NKIVXH.SURFNET@HASARA5.BITNET
                        ROBBEL%NKIVXH.SURFNET@SARA.NL
                        PSI%02041291011::ROBBEL