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TRS-80 Model 4 PAL Source

H

hexsane

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Mar 4, 2009
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Omaha, NE USA
With the passing of Stan Slater of Computer News 80 in August and the closing of the CN80 store on eBay there is no source for the Model 4 Memory PAL (or any of the other items that were being offered by CN80). Is anyone aware of an alternate source for this part or of the file needed to program the PAL? Anyone familiar enough with this part to recreate the PAL?

-Matt
 
I sent in a request on comp.sys.tandy and see if anyone else might know of an alternate source. I didn't Stan had passed away! :( Really a great guy to deal with. Always courteous and friendly. Got my 15meg HD from him along with a bunch of other parts.
 
Since it is replacing a 20 pin dip shunt, can it be that hard to decode manually? I'll have to look at the various model 4 computers I have and see what they havin in U72.
 
mditto said:
I downloaded a crusty old FORTRAN program called PALASM20 and used it to compile the specification into a JEDEC file. I hope it worked and it's
the format you can use.
Click to expand...
Mike,
Does your compiled program run on MSDOS or Windows? I have been looking for an old version of PALASM. The only old version I have is part of a Data I/O PROM Programmer system, but I would like a DOS version.

The newer versions of PALASM that are available on the net have a more powerful command structure to support larger devices, but lose the simplicity of the original. For instance it no longer supports the key word "Function Table" for generating test vectors.

I assembled your PAL Design Specification using the Data I/O with a LogicPak and a 303A-100 PALASM Design Adapter and got the same fuse map and an equivalent JEDEC file.
-Dave
 
Any solutions for this? I am in current need of such a chip.

And failing that, what would I need to read/burn these myself? On the cheap preferably!
 
Last edited:
Well, some little advance here...

I've successfully (theoretically) converted the U72 JEDEC file (I suposse that it's a PAL JEDEC file) to a GAL one using an old MS-DOS PAL2GAL.COM tool. Source device has been defined as PAL16L8 and destination GAL16V8, I'm pretty sure that they are compatible, at least looking at the info I've found across the web.

I've tried also some others tools (PALTOGAL.EXE from Laticce and the one from Opal Jr suite) with no luck, the only converted file that my EPROM programmer (a Genius G540) accepts as a valid GAL16V8 file is the first I mention.

Now I need some GAL chips to try and program them with this file :)
 
One more entry...

I've programmed a GAL16V8B with the converted U72 JEDEC file (using PAL2GAL.COM); but after upgrading the Model 4 adding the new 8 RAM ICs and replacing the shunt at U72, it only shows a garbage screen. As I've tested the RAM ICs swapping them with the original 64K, seems that the GAL is the culprit of the non working upgrade. It can be a wrong original U72 JEDEC file (no old feedbacks about it?), my programmer going bananas with that file/IC or simply the GAL16V8B not being the right GAL to fill U72.

I'll try to gather more info about PALs and such, maybe it's time to get a PAL programmer and use a real PAL chip....:angry:
 
The Xeltek Superpro Z ended up not being able to do PAL as I thought. Should have made a specific inquiry to the mfg instead of trusting others posts, my bad. Well now I have an Advin Systems Pilot-MVP on the way which should do the trick, however I'm spending more on this memory upgrade than I did on my modern gaming rig's memory! I was hoping to be able to provide these cheaply, but I may have to charge a little to recoup some expenses. That said I am hoping this coming weekend to get the job done, if my new programmer isn't doa!
 
I'm interested in this PAL programmer, if you find that it works, let us know.
I'm starting to think that the PAL2GAL converter used doesn't make a proper conversion, I've used all the other tools and they usually give a "better look" JED files. Even Opal Jr has a neat equation generator that gives enough clues to think that I'm stuck in the conversion procedure.

As my main GAL programmer is not able to program the other JED files, I can try and old Willem programmer, maybe it can work with these files.
 
jltursan said:
One more entry...

I've programmed a GAL16V8B with the converted U72 JEDEC file (using PAL2GAL.COM); but after upgrading the Model 4 adding the new 8 RAM ICs and replacing the shunt at U72, it only shows a garbage screen. As I've tested the RAM ICs swapping them with the original 64K, seems that the GAL is the culprit of the non working upgrade. It can be a wrong original U72 JEDEC file (no old feedbacks about it?), my programmer going bananas with that file/IC or simply the GAL16V8B not being the right GAL to fill U72.
Click to expand...

According to my Data I/O wallchart, a GAL16V8B is a Lattice part. So you would need the Lattice version of the pal2gal converter.
I have some AMD PAL16V8's that I can program for you if you have a set of good equations or enough source data to derive the equations.
 
The Lattice converter was my first option; but it seems that it doesn't like the contents of the U72.jed file. I don't remember exactly; but it moans about a too old part or something like that (doesn't support PAL16L8?), no matter what options I try. Maybe with an older version...
Btw, do you mean that you must use the correct brand converter to create the proper GAL file?, if so, as I'm using a Lattice GAL, I'm forced to use the Lattice converter :(
I've derived the eqn file using the Opal Jr suite; but I'm not sure about the result; anyway if you're able to program a PAL using the eqn file I can send it to you, thanks for your kind offer!
 
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