[Coco] Errors in Leventhal's 6809 Subroutines book?

[gene heskett]

On Saturday, January 29, 2022 7:30:26 PM EST Rick Ulland wrote:
> And so, haven't you learned far more than if the book had been correct?
> It's a plot, I tell ya.
> 
> -ricku

Chuckle, but no, Rick, not a plot in that sense, it is far more likely 
the cartogaphers copyright proof, on any map, there is a small town that 
does NOT exist, in the middle of a cornfield or whatever. It is their 
proof they own the copyright when the case comes to trial for damages.

> On 1/29/22 12:17 PM, Don Barber wrote:
> > Hi Michael, I tested both fixes I suggested in my original message at
> > the start of this thread. As others have said there are more
> > efficient techniques but those are the fixes to get Leventhal’s
> > algorithms working as designed.
> > 
> > Sent from my iPhone
> > 
> >> On Jan 29, 2022, at 10:59 AM, michaelkline704 at gmail.com wrote:
> >> 
> >> If anyone comes up with a definitive/tested answer, I would like to
> >> know so that I can correct my copy of the book (if necessary). One
> >> of my desires is to learn ASM for the CoCo.
> >> 
> >> Cheers!
> >> Michael
> >> 
> >> 
> >> -----Original Message-----
> >> From: Coco <coco-bounces at maltedmedia.com> On Behalf Of Robert Gault
> >> Sent: 29 January 2022 00:11
> >> To: CoCoList for Color Computer Enthusiasts <coco at maltedmedia.com>;
> >> robert.gault at att.net; lost <lost at l-w.ca> Subject: Re: [Coco] Errors
> >> in Leventhal's 6809 Subroutines book?
> >> 
> >> Sorry about that. My cellphone trashed the line feeds. Maybe this
> >> will work.>> 
> >>    ldx ,s    leax -1,s    stx ,s
> >> 
> >> Bad code might be
> >> 
> >>    ldx ,s    leax -1,x    stx ,s
> >> 
> >> Or depending on what is in regS
> >> 
> >>    leas -1,s
> >> 
> >> The comments suggest that regS is a pointer to a 16bit value so the
> >> second sequence should be the correct one.
> >> 
> >> Sent from AT&T Yahoo Mail on Android
> >> 
> >>   On Sat, Jan 29, 2022 at 1:02 AM,
> >>   robert.gault at att.net<robert.gault at att.net> wrote:   Right, I just
> >>   looked up what I think are the lines in question.      ldx ,s    
> >>    leax -1,s      stx ,s The instruction is legitimate but the
> >>   sequence makes no sense to me. The second instruction removes the
> >>   result of the first. The comments with the code suggest that regS
> >>   points to a value which is to be decreased. In that case the code
> >>   should be      ldx ,s     leax -1,x     stx ,sIf regS held a
> >>   value instead of a pointer, then one should just use      leas
> >>   -1,s Sent from my LG Mobile


Cheers, Gene Heskett.
-- 
"There are four boxes to be used in defense of liberty:
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 - Louis D. Brandeis
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