[Coco] assembly language question.

[Arthur Flexser]

Oops, right you are.  Thanks, slipped a cognitive cog.

Art
On Wed, Feb 3, 2010 at 10:42 PM, William Astle <lost at l-w.ca> wrote:

> 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.
>
>
>
>> Art
>> 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
>>> clear
>>> 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
>>> here?
>>>
>>>       cmpx  <LblName memory address in DP that holds the $000A above
>>>       blo     somewhere else
>>>
>>> Thanks.
>>>
>>> --
>>> 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.
>>>
>>> --
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>>>
>>>
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>>
>
> --
> William Astle
> lost at l-w.ca
>
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