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From: aida@porthos.csl.sri.com (Hitoshi Aida)
Newsgroups: comp.unix.wizards,comp.periphs
Subject: Re: 18-bit Device on a MicroVAX II
Keywords: DMA device driver Q-bus
Message-ID: <6002@csl.CSL.SRI.COM>
Date: 26 Jul 88 18:14:35 GMT
References: <349@rhesus.primate.wisc.edu>
Sender: usenet@csl.CSL.SRI.COM
Reply-To: aida@csl.sri.com (Hitoshi Aida)
Organization: Computer Science Lab, SRI International
Lines: 24

In article <349@rhesus.primate.wisc.edu> bin@rhesus.primate.wisc.edu (Brain in Neutral) writes:

>We have built a Parellel DMA Interface in house.  We
>have been unable to read anything from the device although
>I have successful accessed the different registers on the
>card.(I have verified this with a scope)  I get an interupt
>and the word count goes to 0.

I also have made a Parallel DMA Interface for MicroVAX II using
DCK-11 chipkit from DEC.  Functionally, it is just like DWV11-B
(not DWV11-W) and it has only 18 bit address.  I wrote driver
for 4.2BSD(ported to MicroVAX II by us) and transfered it to
4.3BSD with no ploblem.  I advise you to test the DMA function
of your interface under console.  We used our LSI-11/73 to
test our board.

I think we can only use lower 256KB out of total 4MB of Q22-bus
address space under Berkeley-distributed unix.  Maximum byte
count for one DMA transfer is usualy limited to 32767, thus
there would be only a little performance benefit if we modify
ubasetup to handle 22 bit address space.
--------
Hitoshi AIDA (aida@csl.sri.com)
Computer Science Lab, SRI International