Subject: Re: DEC RL02 anyone need one?

From: Al Kossow <[email-masked]>
Date: Thu Jun 5 08:32:33 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.

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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?

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From: [email-masked] (Tony Duell)
Date: Thu Jun 5 08:32:44 2003

> 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