Path: utzoo!attcan!uunet!lll-winken!lll-lcc!ames!mailrus!cornell!uw-beaver!tikal!amc!mikem
From: mikem@amc.UUCP (Mike McGinnis)
Newsgroups: comp.sys.m68k
Subject: Re: addq.w #n,sp and a pop quiz
Keywords: C asm addq cmpa
Message-ID: <810@amc.UUCP>
Date: 14 Dec 88 17:05:24 GMT
References: <5005@bsu-cs.UUCP> <5460@cbmvax.UUCP> <1100@ncar.ucar.edu> <4350@Portia.Stanford.EDU>
Distribution: na
Organization: Applied Microsystems Corp.; Redmond, WA
Lines: 30

In article <4350@Portia.Stanford.EDU>, duggie@Jessica.stanford.edu (Doug Felt) writes:
> In article <1737@oakhill.UUCP> davet@oakhill.UUCP (David Trissel) writes:
> >
> > [stuff deleted]
> >
> >There is only one place in the instruction set where a data register is
> >implicitly sign-extended. Where?
> >
> 
> I believe this instruction is CMPA <ea>,An where a word-length value
> in the effective address field (possibly a data register) is
> sign-extended before being compared with the address register.
> 
> >
> >  -- Dave Trissel  Motorola Semiconductor, Austin Texas
> 
> Doug Felt
> Courseware Authoring Tools Project

The CMPA instruction implies that the destination operand is an address 
register. 
The only place a data register will be extended to a long is the MOVEQ
instruction. The source operand must be no more than 3 bits (37.5 cents :),
and the value gets placed in the destination operand (data register),
then extended to a long.
Do I win a cupie doll???
	Michael E. McGinnis
	Applied Microsytems Corp.

"You wake up lost in an empty town, wondering why no one else is around"
"Look up to see a giant boy - you've just become his brand new toy..."