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Re: MESS Dumping Project ? [Re: Darkstar] #51488 07/07/09 03:24 PM
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Carolynhorn Offline
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Darkstar, oh, nice one! That would be brilliant, if you would do that for us! It sounds very do-able *happy-dance* Mind you, if your place is anything like ours, finding paperwork can be a bit of a nightmare wink

Carolyn

Re: MESS Dumping Project ? [Re: Carolynhorn] #51491 07/07/09 05:43 PM
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Darkstar Offline
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Okay, here's the schematic (full size version here):

You have to figure out the pins by yourself though, sorry for that.

It basically uses 2 or 3 latches (74LS373) to set an arbitrary address to the address lines of the EPROM and then reads back the data through the (EPP) parallel port.

The trick is that you select the a chip via the strobe and select signals. The 74LS138 then enables exactly one of the three 74LS373s, or, if you set strobe and select to 1, it enables the data output of the EPROM so you can read the data back.

Reading a byte goes something like this:

set parallel port to output
set strobe,select to 0
output lower 8 bits of address to lpt
set strobe,select to 1
output upper 8 bits of address to lpt
(
optionally, if your ROM has more than 16 address bits:
set strobe,select to 2
output 8 more address bits to lpt
)
set strobe,select to 3
set parallel port to input
read 1 byte of data from parallel port
...rinse&repeat with the next address

You have to use a DLL for direct access to the lpt port on windows, I used this one.
As soon as I find the source code I'll post it, too.

(for the electronic nerds: yes I know this is not a completely clean design, because at one time there are two chips driving data onto the bus at the same time, but it did work for me...)

-Darkstar

*Edit: For those who are interested, I dumped a few ROMs some years ago before I threw out the hardware. They are available here, maybe they are useful for something in MESS, dunno. The ZIP file contains the BIOS and ROM Debugger from a Zenith XT, two different TurboXT ROMs, an AWARD 286 Modular BIOS (V3.03 NFS 11/10/87), the Phoenix BIOS from a Commodore PC (80386SX BIOS Rev. 1.03), A NetWare BOOT ROM for an ArcNet card (archaic! ;-) and some other harddisk- and floppy-controller ROMs)

Last edited by Darkstar; 07/07/09 05:59 PM.
Re: MESS Dumping Project ? [Re: Darkstar] #51493 07/07/09 08:02 PM
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Guru Offline
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if that diagram had full labels it would be easier to figure out. But as it is, it's too simplistic and therefore not very helpful.
In the pic the chips below are indeed RAMs so just the top socketed chips are needed.
The best idea is to just buy a cheap EPROM programmer like a Willem. You can get those on ebay for $50 or so.
Or dump out the data using some software.
Does that thing have a serial port or some kind of output connector? If so the software dump method would work. Otherwise buy a cheap Willem programmer, pull the chips and read them out. The job could be done in a few minutes once you get a Willem.
If you wanted to build one, this here is more the type of thing you'd need.
http://www.armory.com/~rstevew/Public/Pgmrs/EPROM/AndrewMcCubbin/_ClikMe1st.htm

Those ROMs are 28 pin, so they must be at least 64k. The way I would identify them is to pull the sticker off the EPROM (the brown chip) and then read what type it is. Chances are if you read the others as the same type they would be ok.
Even something using this type of ancient technology is quite complex to build for a novice.
It'd be far easier to just buy a Willem.
Something like this....
http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=310124490071
Just search on ebay for 'Willem EPROM programmer' and buy the cheapest one.

Alternatively you can pull out the ROMs, stick them in a piece of styro-foam and post it to one of the MESS-related people located in England and they could dump it and return them. There are a few people near you.

Re: MESS Dumping Project ? [Re: Guru] #51494 07/07/09 08:36 PM
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Phil Bennett Offline
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Originally Posted By Guru
Alternatively you can pull out the ROMs, stick them in a piece of styro-foam and post it to one of the MESS-related people located in England and they could dump it and return them. There are a few people near you.


Yeah, I'd be willing to dump them for you (I'm based in Newcastle FYI).

Re: MESS Dumping Project ? [Re: Phil Bennett] #51495 07/07/09 08:40 PM
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judge Offline
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I really should take apart that megaduck and send those roms to some of you uk people...

Re: MESS Dumping Project ? [Re: judge] #51496 07/07/09 09:51 PM
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R. Belmont Online Content
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There are also MAME-friendly dumpers in (at least) Italy, Belgium, and Sweden.

Re: MESS Dumping Project ? [Re: R. Belmont] #51497 07/07/09 11:14 PM
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Darkstar Offline
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Now that I took another look I have to agree with Guru: If you can't figure the schematic out (i.e. which pins of the 74LS373s go where, etc.) then you should probably stick with a Willem Programmer. It made (of course) perfect sense to me but then again I thought it up so that's expected.

-Darkstar

Re: MESS Dumping Project ? [Re: Darkstar] #51498 07/07/09 11:19 PM
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Lord Nightmare Offline
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I can figure it out. its simple enough:
the /strobe (db25 pin 1) and /select_in (db25 pin 17) pins from the parallel port are controlled from the pc end, and go to the 74ls138 pins 1 and 2 respectively, and are decoded into one of four outputs; these cause the parallel port data bus to be latched into one of the three address latches OR enable the rom to output to the parallel port data bus.
the 74ls373 latches have pins 3,4,7,8,13,14,17,18 going to the parport bits d0 thru d7 (db25 pins 2 thru 9) respectively, and have pins 2,5,6,9,12,15,16,19 going to (depending on which of the 3 latch chips) rom A0 thru A7, A8 thru A15, A16 thru A23, and finally, pin 11 (LE) of the 74ls373 comes from a 7404 hex inverter, which has 3 inverters used and inverts 3 pins: pin 15 /y0, pin 14 /y1 or pin 13 /y2 of the 74ls138, depending on whether its from the low, middle or high address controlling 74ls373.
(I assume LE of the 74ls373 latches on the rising edge, which is why the inverters are needed.)
Its a reasonably simple design. I can probably make a marginally better schematic, but right now I'm a bit busy, if I get it done I'll post it here.
LN


"When life gives you zombies... *CHA-CHIK!* ...you make zombie-ade!"
Re: MESS Dumping Project ? [Re: Lord Nightmare] #51511 07/08/09 09:11 AM
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Carolynhorn Offline
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Thanks, everyone, for all the replies, including the schematic and the offers of help. You guys are a helpful, friendly bunch! I shall speak to my husband about it and see which of the alternatives he would prefer me to go with. Watch This Space grin

Carolyn

Re: MESS Dumping Project ? [Re: Carolynhorn] #51533 07/08/09 03:40 PM
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Just Desserts Offline
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Carolyn -

I've been watching this thread for the past week or two, and I want to thank you for your interest in contributing to MESS. It makes me really happy when people are genuinely interested in helping out the project. Thank you! laugh

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