Unibus / Qbus bus drivers and receivers

From: Michael Davidson <michael_davidson_at_pacbell.net>
Date: Fri Jun 29 01:38:30 2001

Ethan Dicks wrote:
>
> If you are trying to design a device without the proper handbook and/or
> chip-designer's guide, you are probably going to have lots of hidden
> gotchas appear unless you happen to clone the bus interface of an existing
> design.

Well, I started out intending to do a pretty exact clone of the
standard DEC bus interface, which is when I discovered that some
of the chips just weren't available any more :-(
 
> For COMBOARDs, we used 8641s and DC013s for the UNIBUS products, and the
> real-deal, expensive DC010, DC004, DC005 chips for the QBus product. I
> think I remember seeing third-party boards using 74LS240s for bus buffers,
> but I do not know how well they'd work in a loaded box (or any VAX newer
> than the uVAX-II).

Yes, I thought that a 74LS240 might be OK as a bus receiver so
this sounds plausible. Of course I could always just use 8641's
for everything but this would probably push the chip count up a
bit and right now it's looking as if space will be quite tight
on the particular prototype board that I'm thinking of using.

Thanks for the help.
Received on Fri Jun 29 2001 - 01:38:30 BST