Re: catbox

andre wrote:
> So I was looking at the Atari catbox which seems to
> have been designed for people with no real electronics
> background.... but 'many' posts just say to get a
> hp5004a instead. I have tried to find more info on the
> HP, but have not been very successful.

The HP 5004A is a signature analyser. At its heart, it's a simplified 16-bit
CRC generator -- it takes a stream of clock-synchronised input bits and feeds
them into a shift register (an LFSR to be precise), which compresses the input
down to 16 bits, and does it in such a way that a false input will cause the
signature to mismatch.

It has a clock gate as well - the clock signal you feed to the SA is ignored
until START goes active, then data bits are clocked in until STOP goes active.

> Looking at the
> front of the unit, there does not seem to be a whole
> lot of things to be able to set. So I am wondering,
> using the Gravitar manual as an example, does the HP
> manual clearly explain how to (for instance);
>
> a. TESTER MODE: SIG

"Signature Analysis" mode. Pretty much all the 5004A does :)

> b. TESTER SELF-TEST: OFF

Well, the all-segments-on test display isn't that much use for troubleshooting...

> C. PULSE MODE: LATCHED

Not sure about this one.

> D START: Negative-going edge trigger
> e. STOP: Negative-going edge trigger
> f. CLOCK: Negative-going edge trigger

Sets the SA to trigger on the high-to-low edge of all those signals.

> DBUS SOURCE: ADDR
> BYTES: 1024
> Enter address 0000 with the keyboard~(HP doesn't have
> a keyboard?)
> SET R/W MODE to PULSE and back to (OFF)..

Looks like a RAM test to me... the CAT Box has the ability to feed a data
pattern into the bus and probe the RAM. The signature analyser can't do this;
it's a strictly passive device.

In effect, the CAT box is a combined digital word generator (stimulus
generator, pattern generator... whatever you want to call it), signature
analyser and RAM/ROM tester fitted into a briefcase with a 6502 microprocessor
to watch over everything.

> and on and on.. How would I know what was a comparable
> thing to set on the HP? The above are just examples of
> things that I picked out that I can't find anything
> remotely the same on the HP.. When people talk about
> it, they make it sound retty simple to use on in place
> of a CAT but it doesn't seem so... Is this all in the
> manuals with the 5004a?

The 5004 manual is online at
<http://www.gamearchive.com/General/Data_Sheets/HP5004.pdf>. There's plenty of
other stuff about signature analysis about -- for instance
<http://www.gamearchive.com/Video_Games/Manufacturers/Atari/signatures/>,
which provides lots of info on how it actually works.

If you wanted to, you could probably build a signature analyser -- it really
boils down to a few 74LS logic chips and some 7-segment LED displays. Though
I'd much rather buy a used HP 5004 and put the time saved into troubleshooting
the game board...

Although at one point I was toying with the idea of making up a small-ish
board that could be connected to an Atari game board to do most of the stuff a
CAT box can do, only without the high cost of purchase. The project kinda
stalled after a while -- too much to do, too little spare time to do it :(

-- 
Phil.
lists@philpem.me.uk
http://www.philpem.me.uk/
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