[Coco] assembly language question.
lost at l-w.ca
Wed Feb 3 22:42:54 EST 2010
Arthur Flexser wrote:
> The example seems a bit unusual in that you're comparing a 16-bit quantity
> (the X register) with an 8-bit one (due to the use of the 'less than'
> sign). I'm guessing that that would cause only the LSB of X ($FA) to be
> compared to <$000A (=$0A) with the outcome that the BLO no branch since $FA
> is greater than $0A by an unsigned comparison.
Not correct, actually. That's "direct page" addressing. That has no
impact on the operand size. Only the address the operand is fetched from.
> On Wed, Feb 3, 2010 at 9:10 PM, Gene Heskett <gene.heskett at verizon.net>wrote:
>> Greets all;
>> I've read through the moto programmers manual for the 6809 for the cmp
>> functions, and am still confused. The cmp function is a subtract function
>> where the answer is thrown away, only affecting the CC flags so that a
>> following beq or blo will take the correct jump. But somehow, it isn't
>> which is subtracted from what.
>> Given that regs.x contains $02FA, and that the integer memory location
>> referenced by LblName contains $000A, will the blo take, or be ignored
>> cmpx <LblName memory address in DP that holds the $000A above
>> blo somewhere else
>> Cheers, Gene
>> "There are four boxes to be used in defense of liberty:
>> soap, ballot, jury, and ammo. Please use in that order."
>> -Ed Howdershelt (Author)
>> <cesarb> Damn, every time I spawn, qf-client-x11 locks hard
>> <Zoid> Don't die?
>> <Knghtbrd> good incentive.
>> Coco mailing list
>> Coco at maltedmedia.com
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lost at l-w.ca
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