Jump to content
TI998owner

Wanted Replacement PAL Chip CorComp FDC 1985 rev A U12

Recommended Posts

Hi Group,

Need a little help. This evening , had one of my CorComp

Floppy Disk Controllers fail . Short across main

5 volt Regulator. Tested, replaced the regulator. Found

That the short started in U12 the second PAL chip on the

Board.

,

The chip has FDC-U12 on the label. The chip is a PLS153AN

Printed on the chip itself.

,

Does anyone have replacement PAL Chip Available ? Or does anyone

Have the correct iNFO to program a replacement PAL

For this CorComp FDC ?

,

Thanks in advance for any help or Info getting this repaired.

TI998owner Lee

  • Like 1

Share this post


Link to post
Share on other sites

Good luck on finding the code necessary to program a PAL for any CorComp card. They tended to set the fuses to prevent reading the chips out. If someone had the equations, it would be possible to recreate the necessary JEDEC file, but so far as I know, that data never made it into the wild either. . .

Share this post


Link to post
Share on other sites

Ksarul and I have been talking sporadically for the past several years about setting up a "PAL Repository" for TI peripherals. Between the two of us, we have a handful of PAL JEDEC files. However, there are a bunch of them missing - notably Myarc and CorComp cards. What is needed is folks with the time (and talent) to trace the PAL inputs and outputs to come up with the necessary equations to reproduce the PALs. That is a daunting task. I have the code to do a large number of EPROMs for DSRs and could probably reproduce the PALs if I had the JEDEC files. There are several of us in the community that could do so. Maybe a group effort and a repository on Atariage?

  • Like 2

Share this post


Link to post
Share on other sites

I remember seeing PAL equations in the TI DSDD Disk Controller package, I believe, how close to this model would Myarc and Corcomp stay?

Share this post


Link to post
Share on other sites

Very far... The CorComp floppy disk controller is significantly different, to start with the electronic design that is very very poor. The worst of the FDC controllers for TI-99/4A.

Satellize the PAL chips is quite easy, this board has no buffers... A shame.

Edited by fabrice montupet

Share this post


Link to post
Share on other sites

Is it possible to use the datasheet for the particular disk controller chip, then look at other existing systems that either do have a documented disk controller using the same chip or just looking at what ic's match and what doesn't on a comparable board and by deduction recreate the jedec or a small smd board that could replace it? Just a thought. Like my Foundation z80 card uses the same chip for it's drive access,

Share this post


Link to post
Share on other sites

The CorComp FDC is based on the TMS9901 and WD2793 controllers couple not the Foundation Z80 card or TI and WHT controllers, and there is no schematics around. Without the jedec files or finding non protected PAL chips, the solution could be to study the two ROM chips and make a long work of retro engineering.
Not sure that someone will get on a such project.

Edited by fabrice montupet
  • Like 1

Share this post


Link to post
Share on other sites

Ooops! Typo error. I wanted to say "Myarc controller" and not WHT one.
I forgot to say that there are different revisions of the CorComp FDC, the REV A that has a WD1773 FDC controller and a later revision that has a WD2793. The PAL chips containt is specific for each revision.

Note that the PLS153AN PAL can be replaced by 12L6.

  • Like 1

Share this post


Link to post
Share on other sites

" later revision that has a WD2793. The PAL chips containt is specific for each revision."

 

 

Yes, I have two of the WD2793 version and the side car version with the WD1773 chip inside. As a side note, and the reason I brought it up, was the Foundation Z80 card has the WD2793, built into it, and the circuitry seems to be close, at least from a reasonable perspective. I was going to play around with some WD2797 and WD3765 IC's to see if a home built controller on a protoboard is feasible.

  • Like 1

Share this post


Link to post
Share on other sites

I found a old explain create by paolo bagnaresi how built pal chip for myarc floppy controller.. i enclosed dump of floppy. Hope is usefully for community..

palMyarc.dsk

  • Like 5

Share this post


Link to post
Share on other sites

I found a old explain create by paolo bagnaresi how built pal chip for myarc floppy controller.. i enclosed dump of floppy. Hope is usefully for community..

Nice find. Paolo wrote a lot of information about the Myarc disk controller. I have seen documentation that explains the memory layout, but never his Myarc FDC disassembled EPROM. :(

Share this post


Link to post
Share on other sites

Here i post a dump of disk full of information on myarc fdc controller with assembly source wrote by Paolo Bagnaresi.. i built this floppy take this info from many disk that i have .. at moment is all that i found.. :-)

myarc.dsk

  • Like 5

Share this post


Link to post
Share on other sites

It’s amazing what people have floating around in their drives :-)

  • Like 1

Share this post


Link to post
Share on other sites

Does anyone here, have or know where I could either get 1. A finished product, 2. The plans to build a product, 3. the place to mail two PAL's, for a PAL dumper?

I have been reading at sites like this, http://www.techno-junk.org/and believe the capability to read my PAL's on the CC disk drive already exist.

I blew one of my new CC a couple of months ago, as was stated in a previous post in another topic, some time back, The 9901 was blown and the bottom PAL was damaged on this device.

  • Like 1

Share this post


Link to post
Share on other sites

Does anyone here, have or know where I could either get 1. A finished product, 2. The plans to build a product, 3. the place to mail two PAL's, for a PAL dumper?

I have been reading at sites like this, http://www.techno-junk.org/and believe the capability to read my PAL's on the CC disk drive already exist.

I blew one of my new CC a couple of months ago, as was stated in a previous post in another topic, some time back, The 9901 was blown and the bottom PAL was damaged on this device.

 

Ricky, sent you a PM.

Share this post


Link to post
Share on other sites

Does anyone here, have or know where I could either get 1. A finished product, 2. The plans to build a product, 3. the place to mail two PAL's, for a PAL dumper?

I have been reading at sites like this, http://www.techno-junk.org/and believe the capability to read my PAL's on the CC disk drive already exist.

I blew one of my new CC a couple of months ago, as was stated in a previous post in another topic, some time back, The 9901 was blown and the bottom PAL was damaged on this device.

You're welcome to what I have.

It isn't a 100% solution because I'm still working equations and double-checking my work.

 

Doug

CC_FDC-REV-A PALs.pdf

CC_FDC-REV-A Wire.pdf

post-48993-0-93269400-1551989327_thumb.jpg

  • Like 4

Share this post


Link to post
Share on other sites

You're welcome to what I have.

It isn't a 100% solution because I'm still working equations and double-checking my work.

 

Doug

 

Great work Doug! Have you done a schematic as well as the board layout?

  • Like 1

Share this post


Link to post
Share on other sites

If he hasn't I will, as this is one of the only floppy disk controllers we don't have good schematics for yet. The only one left after this would be the Atronic controller. . .

  • Like 3

Share this post


Link to post
Share on other sites
Posted (edited)

 

Great work Doug! Have you done a schematic as well as the board layout?

Thanks, it's on my list after brute force PAL reading and the ugly K-map minimization to get a JEDEC "equivalent".

Sorry, just trying to prioritize for the community.

 

Doug

 

EDIT: Just got the BOM done + "reader" layout I'm going to try ... wish there was more I could do to prevent any possible damage like adding buffers to inputs.

 

 

post-48993-0-90799400-1552070307_thumb.jpg

post-48993-0-58055300-1552070328_thumb.png

Edited by helocast
  • Like 4

Share this post


Link to post
Share on other sites

Once we have the schematics, it will be quite simple to add the Corcomp controller emulation to MAME.

  • Like 1

Share this post


Link to post
Share on other sites

Thanks, it's on my list after brute force PAL reading and the ugly K-map minimization to get a JEDEC "equivalent".

Sorry, just trying to prioritize for the community.

 

Doug

 

EDIT: Just got the BOM done + "reader" layout I'm going to try ... wish there was more I could do to prevent any possible damage like adding buffers to inputs.

 

 

 

Doug, what are your thoughts behind your design for the PAL 'reader'? Going to try reading it in something like an EPROM programmer? I'm a little confused over what seems like rather complicated connections ...

Share this post


Link to post
Share on other sites

The problem is that CorComp blew the read fuses, so the only way to really generate the right truth table is to run through all of the possible inputs and look to see what comes out. . .this is pretty much the same problem we have with all third-party cards/cartridges that use PALs.

  • Like 2

Share this post


Link to post
Share on other sites
Posted (edited)

 

Doug, what are your thoughts behind your design for the PAL 'reader'? Going to try reading it in something like an EPROM programmer? I'm a little confused over what seems like rather complicated connections ...

 

Nothing overly complicated and I modified it down once again in implementation to reduce the file size/permutations for somebody that wants to pick up the project from here.

My methodology here was to use both a TL866II+ and GQ 4x4 programmer (for redundancy, both set to slowest "read" setting possible) in a "27C020 (256Kx8bit EPROM) device mode" using address lines A0-A11 as PAL inputs and D7-D2 as PAL outputs (see reader jpg).

By using the 12 LSbits of the 18 programmer outputs one has to analyze only the first 4096 lines of each bin file. In similar fashion, by using the arbitrary 6 MSbits of the data bytes I weeded out the two unused bits by anding with 00111111 (see reader jpg).

 

It isn't a final solution:

- no logic minimization of raw PAL outputs

- no PAL output equations, hence no JEDEC fuse programming file

- no schematic like everybody wants

 

Takeaways:

- PAL FDCU6 logic is the more complex/active of the two based on byte changes in the output file I analyzed (two inputs are from self outputs, three inputs are from outputs of other PAL FDCU12).

This is a poor man's feedback and introduces more logic delays, unlike a registered GAL which provides internal feedback into the input logic.

- PAL FDCU12 logic seems minimal based on byte changes in the output file I analyzed OR I have a malfunctioning FDCU12 chip as well. ¯\_(ツ)_/¯

- I have concerns that FDCU12 is using a clocked signal as a logic input (similar to a registered GAL). It is quite possible the original creator constructed a flip flop(s) out of internal combinatorial logic to further muddy the equations.

- A final thought, it may be possible to use the process I used with BOTH PALs interconnected per schematic to get a combined output (except one would have 1 extra "bit" output to deal with) for a new design using a small CPLD or even the more commonly available PALCE22V10.

- I don't have the software tools nor the time right now to minimize the outputs into equations.

 

Attached ZIP file contents:

PAL12L6-FDCU6 BIN file Reader output raw

PAL12L6-FDCU12 BIN file Reader output raw
FDCU6 TXT file Reader output reduced. Bytes AND'd w/ 00111111
FDCU12 TXT file Reader output reduced. Bytes ANDed w/ 00111111
8Kx8 ROM DevID-06A0_Bank1 BIN file Not sure if original or MG EPROMS
8Kx8 ROM DevID-D1E4_Bank2 BIN file Not sure if original or MG EPROMS
reader JPG file Methodology used to extract PALs content to BIN
Corcomp_FDC-REVA PCB file ExpressPCB 7.8.0 design from physical PCB
PAL12L6 FDCU6 worksheet JPG file Fuse/input worksheet
PAL12L6 FDCU12 worksheet JPG file Fuse/input worksheet
PEBcontacts JPG file PEB I/O pinout
PAL12L6NC PDF file National Semiconductor Datasheet

post-48993-0-41462000-1552355518_thumb.jpg

Edited by helocast
  • Like 1

Share this post


Link to post
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

Loading...

  • Recently Browsing   0 members

    No registered users viewing this page.

×
×
  • Create New...