DEC RL02 anyone need one?

From: Tony Duell <ard_at_p850ug1.demon.co.uk>
Date: Wed Jun 4 19:02:00 2003

> I already have copies of those, and IIRC, they don't have any specs on the
> control 'messages' passed between things, a PROM dump, or anything else
> that is helpful for figuring out how to send commands to the drive.
>
> ---
>
> Sounds like Tony has figured this out already to build the test box.
> Would you be willing to publish the info that you've figured out, Tony?

Of course... I don't keep secrets from the classic computer crowd :-)

The stuff below is all from memory, so I might be mistaken about
something. Much of it was obvious to me from the printset for the
controller and drive, though, and to be honest, if you can't figure out
the details from said scheamtics I don't think you'll be able to design
your own controller.

Firstly remember I was only trying to move the head around and request
status. I didn't actually try to read or write data. I do know that the
data interface to the RL is a low-level one, essentially the bitstream
to/from the head, so the controller hss to separate data and clock, work
out what sector it is, etc. That bit I didn't attempt.

The interface is all differential TTL-level-ish signals. I think I used
26LS31s as drivers and 26LS32s as receivers.

The controller also has to supply the 'energiser' clock. This is a
somewhat odd freqeuncy IIRC.

To send a command, you send a 16 bit serial bitstream to the drive. Some
of the bits are the 'cylinder offset' (how far to move the heads),
another is the direction, yet another is the side select bit. IIRC, the
order of bits is exactly as given in the programming information for the
RL11 controller.

To request status, you send it a command with a particular bit set. The
drive then sends 16 bits back to the controller. What you get is, again,
exactly as documented in the programming manuals.

I will dig out the details of the strobe signals, etc to send/receive
commands.

That should be a start, anyhow

-tony
Received on Wed Jun 04 2003 - 19:02:00 BST