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

[Joel Rees]

(cough)

2022年1月29日(土) 12:34 Joel Rees <joel.rees at gmail.com>:

>
> 2022年1月29日(土) 11:23 Robert Gault <robert.gault at att.net> said:
>
>> A Google search did not find corrections for the book. However, the
>> second error would have been quickly found if EDTASM had been used to
>> compile the code. It would have been reported as an error.
>>
>
> Are you sure?
>
>   LEAX -1,X
>
> is valid syntax for a valid op-code.
>

And so is

   LEAX -1,S

which was causing the problem in the code.

(Which shows why I shouldn't be too critical of Leventhal's books. They
aren't perfect, but neither is my work.)

Sent from AT&T Yahoo Mail on Android
>>
>>   On Fri, Jan 28, 2022 at 8:50 PM, Don Barber<don at dgb3.net> wrote:   Hi
>> folks, I've been teaching myself 6809 assembly, and quickly ran
>> across Leventhal's books which have been invaluable. I have the
>> programming book, but have also been referencing the subroutine book
>> from online copies available at:
>>
>>
>> https://colorcomputerarchive.com/repo/Documents/Books/6809%20Assembly%20Language%20Subroutines%20(Lance%20Leventhal).pdf
>>
>> and
>>
>>
>> https://archive.org/details/assembly-language-subroutines-for-the-6809_Leventhal
>>
>> Both appear identical.
>>
>> However, I've already run across two bugs:
>>
>> One is on page 72, in MPBMUL, where a BNE is executed right after a
>> "LEAU -1,U". However, the LEAU does NOT set the Z flag, so the BNE is
>> actually working off either the preceding INCA or the STA instructions
>> (depending upon the STA's Carry result). One can test this does not work
>> by trying to multiply 0x0001 times 0x08a6; the result will be an
>> incorrect 0x00a6. One has to add a 'CMPU #0' after the LEAU statement to
>> get the correct behavior.
>>
>> The other is on page 78 in MPBDIV, where one will find a "LEAX -1,S"
>> that should instead be "LEAX -1,X" as the X register is being used as a
>> decrement counter. The original text will result in an infinite loop as
>> the S register is not modified in this loop.
>>
>> So my question is: is there an errata somewhere where known bugs are
>> listed? I imagine people ran across these back in the day too. Both of
>> these got me stuck for an hour or three each, though in hindsight they
>> should have been obvious.
>>
>>
>> Thanks,
>>
>> Don
>>
>>
>>
>>
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>