RE: [SEGA Space Ship] Some update...

From: Bill <>
Date: Tue Feb 23 2010 - 08:28:59 EST

Those 2101s fail quite often on just about every board that uses them. I
would socket and replace that third one as preventative maintenance
regardless of whether or not it is bad right now, especially if the two
others failed.


-----Original Message-----
[] On Behalf Of Andrew Welburn
Sent: Tuesday, February 23, 2010 3:46 AM
Subject: Re: VECTOR: [SEGA Space Ship] Some update...

Sounds like good work!

A few things though.. it sounds like your sound board is bad, if i read your

message correctly, you are saying that the game works in attract mode, but
there is a constant noise? the only thing you can hear is the fire noise
when the button is pressed? It sounds like all sounds are 'on' and enabled
at the moment.

I would say your sound board, or the sound control latches are bad, i would
not say you have a ram problem at all ?

but.. on a side note, (i know nothing of CCPU workings) does the ccpu not
have 'internal' registers for its own math functions that you can use as
temporary storage for ram checking routines? I wrote a ram checking routine
for Galaxian pcbs that worked without using any ram at all, i used the
internal cpu registers creatively when i needed temp. storage instead. (this

was all on a z80, and i don't know how 'slimline' the ccpu is) Does the CCPU

have a status flag register? i'm sure its possible ;)

Andrew Welburn
----- Original Message -----
From: "Fabrice GIRARDOT" <>
To: <>
Sent: Tuesday, February 23, 2010 8:04 AM
Subject: VECTOR: [SEGA Space Ship] Some update...

> Hi all.
> This is an update to my Sega Space Ship fixing task.
> The PCB is a 99% clone of Cinematronics's Space Wars.
> Some weeks ago, I could successully fix the PCB.
> For the first time I could see the game picture... :-)
> Only player #1 's fire button was not working.
> I quickly checked that the button itself was wrong.
> So I simply removed it from the panel, open it and
> fix it.
> When I powered again the game, bad sound could
> be heard and no picture was displayed...
> Scope says the PCB is reseted again by watchdog timer !
> When I press a fire button, fire sound can be heard
> which is good but abnormal when game is not credited.
> I highly suspect the last chip of RAM (I already changed
> 2 bad chip of 3).
> This time it'll more difficult to have proof of a bad RAM,
> because CCPU is able to execute a lot of instruction before
> failing/looping.
> Last week-end, I wrote a software tool called an "assembler"
> for the CCPU planet.
> This tool reads a input text file called "source code",
> generally written by hand. In this file CPU instructions
> are written in an (almost) human readable format.
> The tool writes corresponding CCPU hex opcodes to a binary
> output file.
> This binary file is to be written into an EPROM.
> I'll spread the tool source code under the GPL license.
> Now, I'm writting my own CCPU program to test RAM chips.
> It's not that easy because one would need little RAM storage
> to test RAM.
> So my program test at first 2 RAM storage before being able
> to test the whole banks & addresses.
> Since I can't ouput anything as debug display, if a bad
> RAM storage is found, my program makes CPU jumps to an
> infinite loop doing :
> 1: read last RAM storage to B accumulator
> 2: read any input (so activate signal /READ)
> 3: reset watchdog timer
> 4: jump to 2
> If my CPU is caught in this infinite loop, I'll use the DSO
> to find what is the current selected RAM bank & address.
> "I" register stored in chips I12 & J12 will give me this info.
> By comparing A & B registers, I'll kown what was wrong.
> If all RAM storage is found good, then 2 possibilities :
> A/ my test is incomplete ;-)
> B/ something else is wrong
> In case of (B), I'll write an other program that makes CPU
> execute every possible instruction and I'll check them with scope.
> I already scanned and converted to PDF all the SEGA
> documentation I have.
> The PCB pinout file is updated.
> The screen pinout file is in progress.
> To be continued...
> --
> Fab
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Received on Tue Feb 23 08:29:05 2010

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