[Coco] Bug in VCC ???

Bill Pierce ooogalapasooo at aol.com
Wed Apr 16 14:35:34 EDT 2014


It runs on my Coco 3 so it must be bugged to run bugs... The actuall Coco was always forgiving of us "buggy" programmers... We got away with a lot that wouldn't fly on any other machine :-)

Still playing Zork 1.... Nice job!
Post the link when ya get it fixed and I'll overclock Vcc so it won't be sooo slow in responding....


Bill Pierce
"Today is a good day... I woke up" - Ritchie Havens
 

My Music from the Tandy/Radio Shack Color Computer 2 & 3
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E-Mail: ooogalapasooo at aol.com




-----Original Message-----
From: Luis Antoniosi (CoCoDemus) <retrocanada76 at gmail.com>
To: CoCoList for Color Computer Enthusiasts <coco at maltedmedia.com>
Sent: Wed, Apr 16, 2014 2:24 pm
Subject: Re: [Coco] Bug in VCC ???


Ok, found the culprit. The VCC seems to be fine.

            andb    ~(NF|HF)

should be:

            andb    #~(NF|HF)

my bad :/

and maybe MESS has a bug in the half carry.




On Wed, Apr 16, 2014 at 1:57 PM, William Astle <lost at l-w.ca> wrote:

> On 14-04-16 11:46 AM, Luis Antoniosi (CoCoDemus) wrote:
>
>> I found VCC does Half-Carry different from 6809.
>>
>> doing this:
>>
>> ldd #$0fc9
>> addb #$40
>> adca #$00
>>
>> it will set the HC on VCC but not on 6809.
>>
>>
> I would have expected the 6809 to actually set H in this case. The
> references I have available say it should. After all, you do have a carry
> from bit 3 to bit 4 during the ADCA.
>
> Still, the H flag is only used by DAA. I would be surprised if it is the
> problem in this case (unless the code that's failing is using DAA somehow?)
>
> --
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>



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