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Originally Posted By seanriddle
Kevin- Are you putting VDD on the Rockwell MM78 test pin, or a different voltage? I got an MM75 as well as the MM76EL, and I'm not getting anything from either of them. I've tried several different voltages on VDD and the test pin.


These are MM78's and not the L version. they run on 15V (or -15V depending on your perspective). I connect ground to pins 4 and 6, then 15V to pin 7, and finally 12V (via a pot between ground/15V) to pin 8.

5 connects thru a 56K resistor to ground, clock goes into pin 3 at 15V swing levels, and there's another output at 15V levels driving reset. The 8 RIO lines are pulled to ground thru 22K resistors and that's where the data should appear.

1 byte per clock, starting at address 3C0h (reset vector) 4-5 bytes after reset.


dumping news:

I got 7 more games today, with a total of 9 CPUs inside. two games have dual CPUs (sound + game CPU). I have dumped 7 of these CPUs... one COP411, HD38820, HD38800 (two), D552C (two) and D553C.

Got a D1771-11 and D7528 which will be 'fun' to dump/RE. I am not sure if I can get them to dump but I will give it a try some time soon.

The D1771 is a bone of contention up to this point since not a single document about it to speak of has ever been found, just a patent and a few other scraps. The D7528 has no test pin so I will have to try and coax it into test mode by trying a few things like pulling pins above 5V thru a resistor and seeing if it has a protection diode or not. (no diode = likely test pin sometimes).

The ROM dump production line is really moving in full swing now. I have 18 games now using the HD388xx parts which we still need opcode bit docs for.


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Kevin- thanks for the info. The MM75 is also a 15V part. I had hooked it up like you said, except I'm not sure if I tried 12V on the test pin. When I get some time tomorrow I'll try that.

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I dug through some old electronics of mine and found a Video Technology Mini Wizard game, copyright 1987.

The chip is labelled:

VTEL27-0693 JAPAN
4270N9211 9018H

Anyone know what this is?


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I don't know it. What package is it in? 24, 28 or 40 pins, DIP or skinny DIP, etc. Figuring out what pins are power and ground, and, if possible, oscillator input (resistor to one power rail and capacitor to the other is typical) would help, too. If you can, a scan of both side of the PCB would be useful.

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Do these show you what you need?

https://www.flickr.com/photos/53002952@N03/16231008273/in/photostream/player/

https://www.flickr.com/photos/53002952@N03/16663590970/player/

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Yeah, that's pretty good. So a 28-pin SDIP, but likely not a TI chip- looks like ground on pins 14 and 15, and +6v on 28. Maybe caps for the oscillator on pins 1 and 2? Pins 10, 18, 20-23, and 26 unused.

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Originally Posted By kevtris
(...) I have 18 games now using the HD388xx parts which we still need opcode bit docs for.

It's getting pretty close to working already. Entex Galaxian2 and Pacman2 do their little jingles(off-tune:P) and are controllable.

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Originally Posted By hap
Originally Posted By kevtris
(...) I have 18 games now using the HD388xx parts which we still need opcode bit docs for.

It's getting pretty close to working already. Entex Galaxian2 and Pacman2 do their little jingles(off-tune:P) and are controllable.


Ah nice, that's a lot farther along than I thought it'd be! Well there's plenty of test cases now...

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Well I figured out how to dump the D1771 chips. Just call me the ROM whisperer... turns out it's stupidly easy.

Fire up the chip, apply a clock, and pull pin 17 high. The ROM will now come out pins 5-1, then 28-19.

512 words come out followed by 3.5K words of 0's, which is exactly what you would expect because the PC is 12 bits. There was an unreleased? version of the chip with all 4K on it. This one only has 1/2K though.

1 word comes out for every 8 clock pulses. Reset will reset the PC back to 0.

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Sweet! Gotta love those easy ones. Of course, they are only easy because of your expertise. You obviously don't get frustrated as quickly as I do!

I saw a reference to the D1771 here: https://www.facebook.com/2kboffun

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