Path: utzoo!utgpu!watserv1!watmath!att!bellcore!rutgers!ucsd!swrinde!cs.utexas.edu!uunet!mcsun!cernvax!chx400!ethz!stp
From: stp@ethz.UUCP (Stephan Paschedag)
Newsgroups: comp.os.os9
Subject: C-problem
Message-ID: <4357@ethz.UUCP>
Date: 3 May 90 19:29:50 GMT
Reply-To: stp@bernina.ethz.ch.UUCP (Stephan Paschedag)
Organization: ETH Zuerich, Switzerland
Lines: 19


Hi folks !

I'm trying to access a peripheral device from C-language. The problem I have
is that if the 8-bit data written to the port is 0x00, the compiler generates
a 'clr.b' instruction, which is (who knows why) a read-modify-write operation,
i.e. the CPU first reads the address, then clears it. But I'm not allowed to
read this port during a write operation (I have to do several writes to that
port without any read inbetween !!).
Has Microware ever thought about that problem ? I think many people writing
device drivers in C-language will have similar problems.
Is there a way to solve the problem without using inline code ?

==============================================================================
OS/2 & PS/2 : half an operating system for half a computer

Stephan Paschedag           paschedag@strati.ethz.ch  or  stp@ethz.UUCP
MPL AG, Zelgweg 12, CH-5405 Baden-Daettwil     ..!mcvax!cernvax!chx400!ethz!stp
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