Path: utzoo!utgpu!attcan!uunet!cbmvax!daveh
From: daveh@cbmvax.UUCP (Dave Haynie)
Newsgroups: comp.sys.cbm
Subject: Re: 6551 interfacing
Message-ID: <6970@cbmvax.UUCP>
Date: 24 May 89 21:21:20 GMT
References: <2284@botter.cs.vu.nl>
Organization: Commodore Technology, West Chester, PA
Lines: 27

in article <2284@botter.cs.vu.nl>, rcwlobe@klipper.cs.vu.nl (Reg Lobee) says:

> In article <6925@cbmvax.UUCP>, daveh@cbmvax.UUCP (Dave Haynie) writes:
>> I suspect that you're having setup time problems.  Basically, you can't
>> just hook a 6526 up to the expansion bus and expect it to work OK.  

Whoops, that's supposed to say 6551, not 6526.  The 6551 has an address to 
PHI setup requirement of 90ns.  The timing on the 6526 is much easier to
deal with, meaning that even if it's not quite correct, it'll usually work
just hooked up directly.  I don't recall the exact setup time for the
6526...

> I have connected an 6526 directly to my computer and it works like
> a charm. I use it as an I/O cartridge without any problems so far.

It's important to know that just because something works in one given
situation, it's not necessaily going to always work.  The 90ns setup
for the 6551, for example, is a worst-case figure.  Some parts may only
require 75ns, or even less.  However, if you give it 90ns, every single
part will work.  For home hacking, if it work, do it.  For a commercial
product, you'd better be sure it'll always work.

> |^^\   | Reg Lobee        |==================================|
-- 
Dave Haynie  "The 32 Bit Guy"     Commodore-Amiga  "The Crew That Never Rests"
   {uunet|pyramid|rutgers}!cbmvax!daveh      PLINK: D-DAVE H     BIX: hazy
              Amiga -- It's not just a job, it's an obsession