[stella] Question about Circus Atari and BCD addition

[Andrew Davie]

http://forum.6502.org/viewtopic.php?start=15&t=778
Sounds like a bug to me.
Cheers
A


-----Original Message-----
From: stella-bounces at atari2600.org [mailto:stella-bounces at atari2600.org] On
Behalf Of Dennis Debro
Sent: Wednesday, 20 June 2007 1:02 PM
To: 'Atari 2600 programming list'
Subject: [stella] Question about Circus Atari and BCD addition

Hi there,

Circus Atari is on my "to do" disassembly list. I had a little time so I
started looking at it again today. I think I found a bug but I'm not sure.

In the program when the player hits a balloon the score is tallied into a
variable. Later this variable is used to increment the score. The issue I
see is this tally is not done in BCD but the score is. 

For example, the player gets 10 points for hitting a red balloon. When this
happens the tally variable is incremented by #$0A. Later this gets added to
the player's score using BCD. Wouldn't this cause an error or does the
processor know that #$0A at that point should be #$10?

I haven't looked deeper in the code to see if this is handled. I just
stopped here because it was kind of odd.

Take care,
Dennis



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