FAILED: WD1772-02 floppy controller dissection

[ttlworks]

This is a failed/abandoned dissection of the WD1772PH02-02 floppy controller.

The WD1772-02 was used in CP/M capable Commodore floppy drives:
1570: 5 1/4 floppy drive
1571: 5 1/4 floppy drive //1571 is integral part of the C128.
1581: 3.5 floppy drive

The WD1772-02 also was used in the Atari XF551 floppy drive,
in the Atari ST, and in the SAM Coupé.

;---

Because of job related reasons, it became increasingly difficult
for me and Frank to go on with the chip dissections.

After gnawing for half a year on the chip, all on my own and without any help,
it eventually became obvious to me that I had no chance of finishing this.
So I'm just posting the schematics I have so far.
Be aware that they probably contain errors,
and that it isn't sorted whether signals actually are active LOW or active HIGH.

I do not have permission from Frank to give out the picture of the WD1772-02 silicon.
Lab costs for Frank when decapping one chip is 2.5k€+,
vectorizing a chip took him 3+ months for one chip,
he never got much in return when giving away his vectorized chip pictures.

So if you want to continue this dissection,
and you need the picture of the WD1772-02 silicon for verifying my schematics,
you can't get around negotiating with Frank (fhw72) for the price of said picture.

[ttlworks]

Small picture of the WD1772-02:

WD1772-02 areas marked:

[ttlworks]

Decided to split the schematic into three parts:

The obscure 1 Bit Microcontroller:

The clock PLL, which probably is related to patent US4808884:

And the rest:

[ttlworks]

The Eagle 6.4 source of my schematics:

wd1772-02_04_29_2025.zip

(3.75 MiB) Downloaded 170 times

The program memory of the obscure 1 Bit microcontroller:

mc2.txt

(10.06 KiB) Downloaded 120 times

[ttlworks]

And that's all.
From here on, you are on your own.
Good luck and god speed.

[BigEd]

Thanks for doing what you did and sharing what you have - I can see the difficulty, and those costs are quite considerable.

Interesting, from a high level, if there's both a bit serial and a conventional micro in there - that's what was found in the 8271, which was a very large and expensive earlier chip from Intel.
8271 floppy controller reverse engineer journey write-up (stardot link)

Link to the patent (pdf within)
US4808884A High order digital phase-locked loop system

I found a couple of chip topography design patents - not the chip you looked at, but possibly contain clues or hints. Both called "Chip topography for a MOS disk memory controller circuit"
https://patents.google.com/patent/US4549262A/
https://patents.google.com/patent/US4649474A/

[BigDumbDinosaur]

ttlworks wrote:

This is a failed/abandoned dissection of the WD1772PH02-02 floppy controller.

Ah, too bad you can’t finish.  Costs and all being what they are, I suppose at some point it would become intractable.

Quote:

The WD1772-02 was used in CP/M capable Commodore floppy drives:
1570: 5 1/4 floppy drive
1571: 5 1/4 floppy drive
1581: 3.5 floppy drive //1581 is integral part of the C128.

Actually, the integral drive in the C-128D and C-128DCR models is the 1571.

[fachat]

Sorry to read that!

Many thanks for all the work you've done!

André

[ttlworks]

BigDumbDinosaur wrote:

ttlworks wrote:

This is a failed/abandoned dissection of the WD1772PH02-02 floppy controller.

Ah, too bad you can’t finish.  Costs and all being what they are, I suppose at some point it would become intractable.

Actually the stumbling block mostly was real life problems, most of them job related.

Quote:

Actually, the integral drive in the C-128D and C-128DCR models is the 1571.

My mistake, I fixed this.

[ttlworks]

fachat wrote:

Many thanks for all the work you've done!

André, thanks for the kind words.

[L0uis.m]

Hello 0010 all,

ttlworks wrote:

This is a failed/abandoned dissection of the WD1772PH02-02 floppy controller.

I wouldn't call it a failure, it's just about setting (your) priorities,
and in what state would the world be without them ?

Publishing results in this thread might encourage others to pick up and carry on.

[ttlworks]

Hello Louis,

L0uis.m wrote:

I wouldn't call it a failure, it's just about setting (your) priorities,
and in what state would the world be without them ?

Trying to continue would send me into burnout, I'm familiar with the warning signs.
Need to do something different from chip dissections for a while.

L0uis.m wrote:

Publishing results in this thread might encourage others to pick up and carry on.

Over the years I always published everything: the successes and the failures.
Should be standard, because it might help other people's projects.

[BigEd]

If you have to take a rest, take a rest!

[GARTHWILSON]

It always feels good to wrap up a project and call it finished, with all the documentation and so on.  Life changes though, so I understand.  I myself (like probably most people) have projects I never completed.  I can't let it bother me, although I would still like to get back to them at some point and finish them if life allows.  We sure appreciate the admirable work you've done and presented here, ttlworks!

[ttlworks]

Garth, thanks for the kind words.
This really helps.