Path: utzoo!censor!geac!jtsv16!uunet!lll-winken!ames!uhccux!tbopp
From: tbopp@uhccux.uhcc.hawaii.edu (Tom Bopp)
Newsgroups: comp.sys.apple
Subject: Re: Apple 2e doesn't see my 6522's !!
Message-ID: <4781@uhccux.uhcc.hawaii.edu>
Date: 8 Sep 89 17:28:12 GMT
References: <8909060935.aa25446@SMOKE.BRL.MIL> <21981@cup.portal.com>
Reply-To: tbopp@uhccux.UUCP (Tom Bopp)
Distribution: usa
Organization: University of Hawaii
Lines: 51

In article <21981@cup.portal.com> Dick@cup.portal.com (dick a wotiz) writes:
>> 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 VIAs
>> (6522) and I just can't get it to work !!
>
>I remember running into this a while back...  I seem to recall that
>the 6502 applies the address and R/W signals at the start of phi0,
>but the 6522 latches these lines on the same rising edge.
>What I did was delay phi0 by a small amount, by running it through
>four sections of a 74LS04 inverter before running it to the 6522.
>That way, the 6522 had enough set-up time on the address lines
>before latching them in.  You could probably get away with a
>RC delay also, if you don't have enough spare gates to use.
>
>Dick Wotiz                                    dick@portal.com

I saw your note re/ problems with a 6522 interface, and I saw 
Paul Sander's response about the clock.

If you can find it, get a copy of "Apple II Assembly Language"
by Marvin L. De Jong.  It was published by Sams in 1982 and
may be in a library near you.  ISBN 0-672-21894-1, and in our
university library call no. QA 76.8.S63 D44.

Chapter 9 is called "Programming with the 6522".  The following
circuit is shown (but not explained) as part of a wire-wrap
project for the reader on page 221:

        
      CHIP IS 74LS05 or equiv.
        
        +5 V (Apple 25)
        ------------------------------------------
                    |            |               |
                    |            |               |
                   4.7K         4.7K            1K
                    |            |               |
                    |            |               |
            13  12  |     5  6   |    11  10     |
        ------|>-----------|>-----------|>-----------------
 Phi 1 in           |            |               Clock out to
(Apple 38)          |            |               6522 pin 25
                    -----||-------
                       10 pF

If Paul Sanders is right, this is a circuit that may fix you up.

good luck.

tom