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PC 5170 need help with PAL16L8 and 28S42

J

JustClaire

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Jan 15, 2019
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Hello :) im new to vintage computers so sorry in advance. :p
I am currently trying to make a 5179 clone(just for fun) and i have one small problem.. PCAT Technical Reference has these ic's
  1. PAL16L8 as U130
  2. PAL16L8 as U 67
  3. 28S42 as U72
As far as i know, PAL's need to be programmed, and 28S42 is a PROM, so also needs to be programmed...
If anybody knows how to program them(i mean, what data) please tell me, ill appreciate all help :D
P.S. Sorry if im doing smth wrong, its my 2 day of going into vintage hardware :)
 
The data for the PALs could be a problem. AFAIK the PALs have a security fuse that disables someone to read their internal programming. You can still "read" one like a normal (EP)ROM but then you still need some analyzing software to retrieve the functions behind the data.
 
Thank you, there is also the problem that i dont have original PALs on hand so i cant even make the logic table.. ;-;
 
Maybe someone's done the work. More modern GALs (e.g. 16V8) can be used for the PALs, and quiet often a GAL with a bit of jiggering can be used for the bipolar PROM.

But yes, you need to know what was in them to begin with. I suppose you could make a decent guess on them based on analysis of the schematic and their function.
 
Ruud said:
AFAIK the PALs have a security fuse that disables someone to read their internal programming. You can still "read" one like a normal (EP)ROM...
Click to expand...

Since they are combinatorial only, I doubt they are security protected. As you said, you can dump a truth table provided you know which pins are inputs and which are outputs (some are I/O) - which can be inferred from the schematic.

Ruud said:
...but then you still need some analyzing software to retrieve the functions behind the data.
Click to expand...

LogicFriday is a great tool for this. But it seems the author's web-site is expired. Still available on CNET.downloads.

As far as programming, most modern EPROM programmers will also write DIP-socketed SPLDs. I'm a little surprised the logic equations are not already published and well known. Also don't get hung up on PAL vs GAL. The later is just a commercial trademark. Also V series is a superset of L that adds flip-flops. You can use just about any 16V8 as a replacement (such as the common Atmel ATF16V8s stocked at distributors). If there are PALASM equations available, I can convert them to a ATF16V8 JEDEC bit file for you to program (if no one beats me too it). Likewise, if you dump the truth table from the PROM, I'll see if a PAL will fit. I've successfully replaced PROMs on the PCjr motherboard with overhanging 22V10's with ground jumpers before building custom replacement boards that mount a SOIC/TSSOP on a DIP replacement board.
 
But if you don't have the originals, things get harder. I'll wager that IBM blew the security fuses just a matter of routine.

But yes, dumping combinatorial PALs isn't too difficult--see my blog posts on this from a few years ago, using only a parallel port and some random logic thrown together in an evening.

I like to use the term GAL as a generic, be it PEEL or PALCE or whatever. Erasable programmable logic.
 
Last edited:
Thank you, but the main problem is that i dont have the originals on hand and the EMMA has 14l4 dumps instead of 16l8 for some reason
 
There is a reasonable possibility that I can help you with the truth table in a couple weeks...
 
Sorry - took very long until I got some time to work on this... Managed to make highly flexible :) adapter for reading different chips that my programmer can't read directly:

_IMG_0029.jpg

Another issue was to unsolder those chips from my FRU-6489922 motherboard (type 2) without damaging something. At the moment only U130 done. I don't have enough time to check carefully if the reading has any sense - can see some suspicious data... So for now can check the files - would be interesting to hear your opinion...

View attachment U130.zip


I used Minilog software to minimize logical equations...
 
U87 is done. Unfortunately, Minilog can't handle more than 2000 input terms, so just a raw file for now:


View attachment U87.zip

Does anyone know where to get some software that can minimize this file ?
 
Curious, I've been wanting to program these also and just wondering if I would just load these files up in my programmer and burn it or is there more to it?
 
newold86 said:
Does anyone know where to get some software that can minimize this file ?
Click to expand...

Sigh...

eeguru said:
LogicFriday is a great tool for this. But it seems the author's web-site is expired. Still available on CNET.downloads.
Click to expand...

Minimized:
Code: 
ENDCYCn = RES0WS FSYS16' Q4' AIOW' IORn  + RES0WS FSYS16' Q4' IOCS16  + RES0WS Q4' Q1' ;
DMAAENn = AEN2n AEN1n ;
GATE245 = AEN2n XA0'  + AEN2n' AEN1n  + FSYS16' AEN1n'  + FSYS16 AEN1n AIOW' IORn  + FSYS16 AEN1n IOCS16'  + AEN1n XBHE;
DIR245 = AEN1n AIOW'  + AEN2n' AEN1n  + AEN1n XBHE;
DATACONV = FSYS16 AIOW' IORn  + FSYS16 IOCS16'  + Q1'  + AEN1n'  + AEN2n'  + XA0  + XBHE;
 
Sabertooth said:
Curious, I've been wanting to program these also and just wondering if I would just load these files up in my programmer and burn it or is there more to it?
Click to expand...

No, not in this form, meaning the zip file, not eeguru's source level code. It it possible to do a EPROM or FLASH but you have to make sure the circuit it controls is protected from glitches. A PAL has logic in a particular sequence. A ROM may have any combination of address that are changing as glitches on the output.
Dwight
 
I also ran U130 through LF and got the same minimizations.

Code: 
IRQ13 = ERRORn' ;
BUSY286n = 0;
NPCSn = XA3' + INTAn'  + CS287n  + SMIO ;
RESET287 = INTAn CS287n' SMIO' XIOWn' XA0 XA3' + RESET ;

Simplest next step is rewrite the minimization syntax in CUPL and create a JEDEC file for ATF16V8 programming. Those are still available new from most online parts distributors. If you post the pinouts, I can do that if you like.

Many PROM programmers with burn ATF16V8s. If you don't have one, I can burn and send you a few.
 
Dwight Elvey said:
No, not in this form, meaning the zip file, not eeguru's source level code. It it possible to do a EPROM or FLASH but you have to make sure the circuit it controls is protected from glitches. A PAL has logic in a particular sequence. A ROM may have any combination of address that are changing as glitches on the output.
Dwight
Click to expand...

Well, in that case hopefully the ones I pulled off the board are still good. It just would have been nice to have a backup ready just in case. Thanks
 
Chuck(G) said:
Amazing that I did a 14-part blog on this in 2011 and nobody seems to have noticed. :)
Click to expand...

And an excellent blog it is ;-) Unfortunately not easily found with the ton of garbage that's in the blog section, I was looking for that a while back and got miffed at all the crap in there, Then it dawned on me to find one of your post's and click on the blog entries:
 
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