Path: utzoo!attcan!darkover!seachg!jalsop
From: jalsop@seachg.UUCP (John Alsop)
Newsgroups: comp.sys.ncr
Subject: accessing Multibus shared memory
Message-ID: <180@seachg.UUCP>
Date: 10 Jan 90 13:19:49 GMT
Organization: Sea Change Corp.,Mississauga,Ontario,Canada
Lines: 33

We have an old Multibus communications controller (actually a single-board
microcomputer made by Heurikon) which uses shared memory to interface with
the Multibus host. We are trying to get this working on a Tower 600.

The Multibus memory addresses to which this board responds are decoded by a
custom PAL on the board. The problem we have is that we don't know what this 
address range is, other than that it is a 24 bit address.

We tried writing a simple C program that scanned through "/dev/kmem"
looking for a fixed data pattern which we know is on the board, but no
luck.

I suspect that we are not generating the correct "virtual address" inside
the Tower to map onto the Multibus shared memory space.  Does anyone know
how to do this for the 600?  

Note that we are talking here about Multibus memory addresses, not Multibus
I/O addresses. To read a Multibus I/O address of xxxx, one reads the Tower
memory address FFxxxx.  The problem here is how do you read a Multibus memory
address of xxxxxx.

Hope someone can help!

Thanks,

-- 
John Alsop

Sea Change Corporation
1100 Central Parkway W., Suite 38
Mississauga, Ontario, Canada L5C 4E5
Tel: 416-272-3881 Fax: 416-272-1555
UUCP: ...!uunet!attcan!darkover!seachg!jalsop