[Coco] assembly language question.

[Bob Devries]

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

--
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 2:59 PM
Subject: Re: [Coco] assembly language question.



> On Wednesday 03 February 2010, jdaggett at gate.net wrote:

>>Gene

>>

>>The operation is always

>>

>>R - M

>>

>>where R is the register and M is either a second register or memory. CCR 

>>is

>> set according to the results and addressing mode.

>>

>>In your case the MPU would take $02FA and subtract $000A. The subtraction

>> instruction will affect the N, Z, V or C bits. The BLO instruction tests

>> the C bit and will issue a branch if and only if the CBIT = 1. In this

>> case there is no borrow so the CBIT will be zero and no branch taken.

>>

>>james

>>

> Confirming my aged wet ram's memory of it.  Thanks James.

>

> -- 

> 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)

>

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>

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