[Coco] assembly language question.

[Bob Devries]

ok,... another quote:

The assembler automatically selects direct addressing mode if the high-order 
byte of the address matches its internal "direct page." This direct page is 
not the same as the run-time direct pager register; it is an assemble-time 
value. You ordinarily set it to zero, but you can change it with the SETDP 
directive.

/quote
>From the OS-9 Level 1 assembler manual.

Regards, Bob Devries

--
Besides a mathematical inclination, an exceptionally good mastery of one's 
native tongue is the most vital asset of a competent programmer.

Edsger W.Dijkstra, 18 June 1975

----- Original Message ----- 
From: "Gene Heskett" <gene.heskett at verizon.net>
To: "CoCoList for Color Computer Enthusiasts" <coco at maltedmedia.com>
Sent: Thursday, February 04, 2010 4:00 PM
Subject: Re: [Coco] assembly language question.


> On Wednesday 03 February 2010, Bob Devries wrote:
>>Gene,
>>
>>the orientation of the < is importnat of course, and will determine the 8
>> or 16 bit operation.
>>
>>To compare the X register with memory, it would need to read:
>>
>>cmpx >LblName
>>
>>Regards, Bob Devries
>
> I don't believe so Bob.  If you are looking at page 2-2, section 2.2.4
> DIRECT, that book I have assumed for the 24 years that I've owned it, is
> erroneous.  Note that they used the same right arrow to note EXTENDED
> addressing in 2.2.3 immediately above, and since I know the right arrow >
> means extended, the left < arrow must then mean DIRECT.  And it assembles 
> to
> $9C, offsetbyte.  I believe the notation in the level one assembler manual 
> is
> correct.  Lack of an arrow generally means to load or cmp the immediately
> following byte or int, depending on the size of the register.
>
> Simply put, they cannot use the exact same nemonic syntax for 2 completely
> different operations.  It doesn't grok.
>
> -- 
> 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)
>
> Book: "It's not your way."
>
> Mal: "I have a way?  Is that better than a plan?"
> --"Serenity"
>
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