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From: hyc@math.lsa.umich.edu (Howard Chu)
Newsgroups: comp.sys.atari.st.tech
Subject: Re: The movep instruction & a strange display
Message-ID: <1990Nov1.072136.24326@math.lsa.umich.edu>
Date: 1 Nov 90 07:21:36 GMT
References: <1990Oct31.155603.4066@irscscm.UUCP>
Sender: usenet@math.lsa.umich.edu
Organization: University of Michigan Math Dept., Ann Arbor
Lines: 28

In article <1990Oct31.155603.4066@irscscm.UUCP> mlake@irscscm.UUCP (Marshall Lake) writes:
>Greetings everyone.

>I am having a problem with a 68000 program where the screen goes
>kaflooey at a certain point.  I'm not fooling with the screen in my
>code, only the MFP and the sound chip.  The program works ok except for
>the fact that it screws the display.  I've traced the cause of the
>problem down to a movep instruction that occurs during a timer A
>interrupt.  The movep is a weird instruction where it moves every other
>segment (depending upon the mode) of the source to the destination.  Is
>it possible that my assemblers (the only ones I have are MADMAC and the
>MWC assembler, the latter being a real trip of an assembler) do not
>handle the movep instruction correctly?  The same thing happens with
>both of the assemblers.  I've seen the same code in other programs that
>work properly.

I know that incorrect code is generated for movep by both the 2.0 and
3.0 MWC assemblers. (Different incorrect code, too!) However, I'm pretty
sure that MADMAC handles movep correctly. (I've used it a number of times
with MADMAC and never had any trouble.) You can verify the correctness
of the MADMAC object code just by looking at it in the Atari debugger.
If it doesn't disassemble to what you're expecting, mebbe you're behind
a rev or two on MADMAC?
--
  -- Howard Chu @ University of Michigan

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