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Old 19 September 2010, 22:28   #1
Charlie
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PAL Advice

Be gentle with me chaps, PAL's are a new area for me so please forgive stupid questions and don't make any assumptions in your answers...

I'm hoping to 're-manufacture' a circuit board I have - nothing cleaver:
-Look up codes of IC's etc, buy said components
-Study PCB layout, reproduce PCB using transfer technique
-Solder it all up
-Fingers crossed

Now one one of these IC's is an AIMEL AT27C256R. Ok, it's an EPROM - it's about time I bought a ROM-blower.
I can retrieve the contents of the ROM via the host-computer.

But two of them are PALCE 16V8H-25's.
Hmm, PAL's eh?
I think I'm about to come unstuck...

Questions:
-What does one need to program one of these babies?
Some kind of ROM-blower?
or
Are they 'programmed' on the fly from the ROM on power-up?

If the latter that's good, no problem.

If the former - fingers crossed, I have a feeling I'm not going to like the answer...
How does one program one of these?
and
Is there any way to get the 'software' out of the PAL so it may be used to program another?
There's a minimal chance of being able to track down the original files if I can't do this - game over.

Thank you!

Last edited by Charlie; 19 September 2010 at 22:33.
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Old 19 September 2010, 23:03   #2
alexh
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PALs are programmable logic devices. You program them with very basic logic functions chains of AND, OR, XOR etc. etc. written in a high level language.

You will need the contents of the PAL chips. Without that you'll have to reverse engineer their function. You will probably never be able to read them to extract there program as they will have been programmed with the protection bit set (making them effectively write only).

You'll need something like PALASM (Assembler of code for PAL chips) to produce JDEC files and then a PAL programmer like a JTAG device depending on the type of PAL chip.

There is 99.99% NO chance to get the code from these PALs you'll have to either give up, reverse engineer them (not impossible due to their capacity and uber basic boolean functionality) or find the original creator. There is a very, very slim chance they are not protected. Which model are they?

What is it for? For example David Haynie provided the PAL source code for a lot of Commodore parts.
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Old 19 September 2010, 23:43   #3
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D*mn!!!

Thanks alexh for explaining things to me.

It's a little IDE interface card for (shhh, an Arc'). The card itself works fine but these things are in short supply in Acorn-land so I thought a bit of reverse-engineering may be helpful to that community.

Soldering SMT components and making PCB's is not beyond me, even blowing ROMs once I get round to it...
...but actually applying some brian-cells to the job of sussing out how those PALs work and re-doing them? Well beyond me I'm afraid.

Here's some 'foreign p0rn' for you:

Castle (the company who made this interface) are still just about in the land of the living so I'll see what old files are hanging about that they may be happy to part with. I suspect not a lot.

Ho, hum. Next plan:
I have another such board made by Watford Electonics that's based around simpler components which should be easier to 'clone' but the software for it is 'not great'.

What I'm really trying to do is avoid designing my own IDE card from scratch. I'm told for these computers it's a trivial task but doing so will be a big step up for me:
Copying old designs and lightly reworking them with hobbyist projects in mind is pretty-well my level.

Thanks again.

Last edited by Charlie; 21 September 2010 at 21:07.
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Old 20 September 2010, 00:00   #4
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Due to the fact that this is probably a PIO IDE interface (a very very standard interface) it should be fairly easy to decode the PAL functions based on the schematics of the interface.
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Old 20 September 2010, 00:26   #5
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Also PAL(GAL) are quite old and they are not recommended to use - probably they can be replaced by one CPLD - they are usually easier to program when compare to PAL(GAL)
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Old 20 September 2010, 04:44   #6
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Actual CPLD chips are 3.3V only, no use in IDE devices that are 5V. A GAL chip is easy to program on any decent EPROM burner and the inside code can be read if the program "style" is not "mixed".

Check this lovely board for more information!
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Old 20 September 2010, 08:47   #7
pandy71
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Actual CPLD are available in 5 and 3.3V with 5V compatibility, GAL are easy to program only if Your burner support them which means rather more expensive burners than cheap EPROM only.
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Old 21 September 2010, 21:04   #8
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Thanks for the advice chaps - so one can (possibly) retrieve PAL/GAL data...

I have some developing ideas in mind:
Make a new (very simple) 'IDE' board for the Classic Arc based around the Econet connector along the lines of this:
the "classic" simple 8-bit interface
the "schematic"

8-bit IDE for an 8-bit interface hopefully means a simpler design.

Of course these are ZX Spectum specific, but I can't see why the principle would not work with any computer...
...8-bit IDE does mean loosing 1/2 the capacity of the media, but this version
memory mode CF
would get round that problem.

The biggie?
Well, apart from my not really knowing what I'm doing but I think I could dope the hardware out eventually...
...writing/adapting driver software is waaaay beyond me.


And what's this to do with the EAB..? Nothing, sadly.
I'm rambling in public because here there are sympathetic types who are interested in this kind of thing.
It's frustrating that while the Amiga scene is lousy with people who would find such a project trivial to do I don't think I'm up to it (alone). But as far as I can tell I seem to be the only person actively attempting stuff like this with Acorns these days...


P.S.
A 'proof of concept':
More foreign p0rn

An EcoSCSI Interface

All rather more complex that I'm intending but if one can squeeze SCSI through the Econet headers...

Last edited by Charlie; 21 September 2010 at 23:02.
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Old 21 September 2010, 23:03   #9
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Hmmm why not use some inexpensive uC with SD card?

http://avrprojects.info/avr-interfac...sing-atmega16/
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