🚀 go-pugleaf

In article <1992Sep28.115345.26531@isa.de>, schuster@isa.de (Thilo Schuster) writes:
> I'am looking for a functional description of the register set used
> by the UDA50 RA-8X disk controller for the Unibus. It would be nice to
> have the programming guidelines, too. I've got an old PDP11-24 at 
> home and I would like to make an UDA50 compatible SCSI interface (yes,
> I know, it won't be easy...). Could anybody tell me, where I can 
> obtain these information ?

  It isn't actually a register set. There's 2 registers which are used to
init the controller and point it to a communication area somewhere in main
memory. The controller then fetches commands and returns responses using
this communication area. It's similar to the way the TS11 works.

  Designing one of these controllers is quite complex. You'll need to use
either incredibly fast hardware or custom logic to implement some of the
time-critical sections of the protocol. You'll have it a little easier as
you're doing SCSI, not SDI to the drives. However, consider that most man-
ufacturers have had to make several attempts before they got their products
working properly.

  You should be able to pick up a used Unibus/SCSI controller for less than
this project will cost you.

  If you're determined to proceed, you can order various documentation kits
from DEC which describe the MSCP protocol. However, the last time I looked,
there was a hefty license fee involved, and lots of the important technical
sections were replaced by "This section deliberately omitted".

	Terry Kennedy		Operations Manager, Academic Computing
	terry@spcvxa.bitnet	St. Peter's College, Jersey City, NJ USA
	terry@spcvxa.spc.edu	+1 201 915 9381