Re: Atari 6502A NOP adapter

OK Guys,

A 6502 NOP will not produce sig's that match Atari doc's.
Reason is the 6502 takes two clock cycles to do a NOP instruction.
The Cat Box takes one clock cycle.
So you get double readings of each address. All you need to do is make
an NOP using a couple of counter IC's to cycle through the address range
on each clock cycle. Or divide the clock by 2 and use this as your clock
connection for the Analyzer. You can do this with one D type flip flop IC.

Tim

-----Original Message-----
>From: "martin@guddler.co.uk" <martin@guddler.co.uk>
>Sent: Jan 24, 2009 7:38 PM
>To: Technical Tools Mail List <techtoolslist@flippers.com>
>Subject: Re: [Techtoolslist] Atari 6502A NOP adapter
>
>Sorry guys, I should have said, I've got the doc. I've probably got
>the one you're pointing too as well John. But I'll pick it up from TT
>tomorrow if not, thank you.
>
>Nice to see the same people still reading as were here in 2002 as
>well :)
>
>OK. Tomorrow ill put more thought into comparing the two CPUs. The
>only thing that really springs to mind at the moment is maybe they've
>messed with the order of the address lines or something?
>
>The really odd thing is I know for a fact I've fixed centipede boards
>in the past with my 5006.
>
>Incidentally, I'm now using the 9100 for the sigs. I keep meaning to
>post the programs up on my website but they need some refining. Error
>trapping and the like. I've had it producing HP signatures for some
>time now.
>
>I'll post back if I work anything out. Thanks for the pointers though.
>
>Martin.
>
>
>On Jan 24, 2009, at 20:39, John Robertson <jrr@flippers.com> wrote:
>
>> martin@guddler.co.uk wrote:
>>> Hi all,
>>>
>>> Just been trying to find information on what is different about the
>>> KK 6502 (Atari) NOP adapter that makes it produce 8080 signatures
>>> as opposed to the normal 6502 ones and I discovered that the
>>> question has been posed before - not surprising I guess.
>>>
>>> Just wandering if this mystery was ever solved and perhaps I'm not
>>> looking in the right places?
>>>
>>> I'm sure I once took down signatures from a working board using my
>>> standard 6502 adapter but as always, when I want them, I'm damned
>>> if I can find them so maybe I imagined it.
>>>
>>> In case anyone hasn't a clue what I'm talking about, see the
>>> footnote on page 14 of the PDF document "SigAnalNotes.pdf" that
>>> ought to be all over the net but I can't find a link to it just yet!
>>>
>>> The original TechTools list message where this was asked before is
>>> here (with no answer):
>>> http://www.vectorlist.org/TechTools/2002/10/0035.html
>>>
>>> Thanks,
>>> Martin.
>>>
>> Check the FTP archive on TTL (link below) for "Sig-Analy-
>> HPJMay77.pdf" this covers some Sig Analysis questions. I only have
>> info on the 6502, 6800 and Z80 NOP fixtures, which is at the rear of
>> "KK-Signature2.pdf" in the KurzKasch section of TTL.
>>
>> For your question I would print off the last two pages of the
>> KK_Signature2.pdf, then pull up info on the 8080, find out what
>> instruction gives NOP, and then compare the pinout with the 6502.
>>
>> John :-#)#
>>
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Received on Sat Jan 24 21:22:38 2009