I have a couple of these, modified to use with a Tandy Model III or 4. They are very similar to the controllers used inside Tandy's big black box hard drives.
Manual for the WD1002-05 is on bitsavers:
See page 11. It has the same interface as the HDO. I have a WD data book at home with the correct information, but have never scanned it.
Here is info for interfacing one to a TRS-80 model I
And this note, copied from comp.sys.tandy
The WD1002-05 or WD1002-HDO (the second has no floppy interface) was a
general purpose HD interface for MFM drives. It was used in the Kaypro 10,
and possibly other computers. I think that for TRS-80's, it was a hobby
project to make it work. I found the interface to use these with the Model
I and Model 4 on the Dutch Users Group site. I managed to get a couple of
the WD1002 boards and built interfaces for my Model I and Model 4P's. The
interface maps the same ports for I/O as the Tandy systems. The main
difference is that port C0 is not implemented, which is the hardware
write-protect. It was a simple matter to modify LDOS and Montezuma Micro's
CP/M to ignore this port.
on behalf of B Degnan
Sent: Thu 9/24/2009 9:49 PM
Subject: Re: [midatlanticretro] a WD 1002-HD0 controller for Kaypro 10 and such
Jim Scheef wrote:
I believe the 40-pin interface would be early IDE as used by Compaq in
their early desktops.
Another interesting monster emerges from my closet: a Western Digital
WD 1002-HD0 (hard drive only) controller. It's a 40 pin ribbon cable
interface (not ISA or such) that's some parallel interface for a
Kaypro 10. Does anyone need it?
I am guessing it's a little older than that. I bet it was for a Xerox or a early 80's odd-ball system, not DOS based. Just for curiosity, can you take a picture?