Re: A83: rom redundancy

To: assembly-83@lists.ticalc.org
Subject: Re: A83: rom redundancy
From: Scott Dial <wrath@calc.org>
Date: Sat, 29 Apr 2000 03:33:16 -0500
Organization: ByMe Inc. Technologies \ TCPA
References: <20000429081002.62749.qmail@hotmail.com>
Reply-To: assembly-83@lists.ticalc.org

It was done intentiolly... I will give the long explainion because I am
bored. If you were to have to make updates to the calculator rom but yet
not have to reassemble other code how would you maintain locations for
the calls? This is a common problem with a simple resolution. If you
were to use instead a series of pointers that were called instead you
could keep them in the same position but change around the rom. TI did
screw up in that at $4014 the should have just been a jp $268... but
anyways. If you decide, "Hey, I am just gonna call $4014", then you code
will only work on that rom version because from rom version to rom
version the location changes. 

Doug Torrance wrote:
> 
> I was messing around, comparing the disassembled roms of the 82 and 83, and
> I noticed something interesting.  Most of the 83's commonly used rom calls
> in the $4000's actually just call another routine earlier on in the rom.
> For instance, take a look at _getcsc, located at $4014:
> call $268
> ret
> I tested out a little program using $268 instead of $4014, and of course it
> worked perfectly.  Plus I saved a few clock cycles.  Any idea why TI might
> have done this?
> 
> Doug
> ________________________________________________________________________
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-- 
Scott "_Wrath_" Dial
wrath@calc.org
ICQ#3608935
Member of TCPA - tcpa.calc.org
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References:

A83: rom redundancy

From: "Doug Torrance" <profzoom@hotmail.com>