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From: edstrom@elmer.hsc.ucalgary.ca (John Edstrom)
Newsgroups: comp.os.os9
Subject: linking to absolute addresses
Message-ID: <1991Jan24.162635.1742@yogi.fhhosp.ab.ca>
Date: 24 Jan 91 22:26:34 GMT
Organization: Dept. Clinical Neurosciences, U of Calgary, Alberta, Canada
Lines: 33
Nntp-Posting-Host: elmer.hsc.ucalgary.ca

Is there anyway to link a module to an absolute address?

The reason I ask is that the device I am writing a driver for
(Data Translation's 1492 AD/DA & etc board) has 1/2 Meg of dual
ported memory on board.  Idealy the user program would be able
to read/write from the DT1492 memory while the device is acquiring
data.  My problem is accessing the memory from a program without
going to system mode.

I tried using colored memory but the os dumps about 12 bytes of
important stuff at the bottom of the memory section when I request it
from the system.  Since there lots of bytes around the loss of data
space doesn't bother me much.  However, the ADC will writes data over
these magic numbers and all attempts to access that segment of memory
fail with a buss error.

The easiest way I can think of is to create a non-relocatable data
psect and then link my program to it.  But I can't see how that is
possible.

An alternative would be to jump into system mode, copying the data I
wanted into a user-space buffer, returning to user mode and continuing
with the data manipulations.  Although my real-time application will
probably not suffer from this it seems like a barbaric thing to do.
Is there any way around this impasse?

John  Edstrom    |    edstrom@elmer.hsc.ucalgary.ca

--
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