Re: Signature Analyzers

From: Matt Rossiter - Verio Southern California <matt@rossiters.com>

>I may have asked this before on Vectorlist, but how exactly do you
>generate the proper signatures on Atari boards without the CAT
>box? Do you hardwire the data lines on the CPU to something specific?

It depends what you want to fix. Most Atari boards have two "sides",
the front end (CPU/ROM/RAM/GLUE) and the "video" section.

For the "video" section, the manual tells you where to connect the
str/stp/clk lines and how to put the board in SA mode.

For the front end, you need at least one more piece. Either:
1) A CAT box
2) An HP CPU test jig
3) A NOOP CPU jig
4) A home made test jig

Most people don't have a CAT and/or don't want to pay $500 for one.
I have yet to see a real HP test jig.
I found the NOOP to have an unstable clock and I never hooked the logic
analyzer up to it to find out why, although I thought about it.
So finally, I made a test jig that plugs into the CPU socket
and generates the correct signals (with a clean clock) to do SA.

However, there are better ways to trouble shoot a uP system in
the '00s and not all of the reasons for using SA are still valid.
Back in the '70s and early '80s, SA was a good because:
1) EPROM programers were expensive and rare
2) We didn't have a checksum reference
3) We didn't have ROM images for all the ROMs of all the games
   on a PC in front of us
4) RAM testers were rare and expensive

SA was handy because it allowed you test a game ROM *WITHOUT*
requiring any of that hardware. All you had to do was read the
sig on each pin of the ROM and you knew if it was working.
SA also allowed you to easily test RAM without additional h/w.

Today, I find it much quicker to just pull the ROM out, read it,
verify the checksum and even the image, than to set up the SA
and read each pin on each ROM.

For the glue and RAM, I use the fluke.

But... For the "video" generator, you can't beat SA.
It is definitely the easiest and fastest way to go.
Best of all, no additional hardware (noop cpu, etc)
is required.

>
>Where do the stop/start/clock wires go?
>

Where the manual says to connect them.

>
>Just curious.
>
>
>Matt
>
>
>
>_____________________________________________________________________
>
>On Fri, 14 Jan 2000, Mark Shostak wrote:
>
>> > Is it true that the it reports the same signature as a cat box?
>>
>> Yes, the HP reports the same signatures as the CAT box.
>>
>> However, the HP is a lot nicer to use. I have both and for SA
>> I use the HP over the CAT. It has better probes, a bigger display,
>> it's like a bench meter in that you can read it while your working,
>> on the CAT, the display is oriented up, towards the ceiling,
>> so you can't just glance over at it to read the sig.
>>
>> -Mark
>>
>>
>
>
Received on Fri Jan 14 16:42:29 2000