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fixed inverse use of carry in SBC

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James Tauber 2011-08-06 23:53:47 -04:00
parent 6e709fcc4c
commit 8f10724a7f
1 changed files with 2 additions and 2 deletions
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applepy.py
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@ -620,10 +620,10 @@ class CPU:
m1 = (m1 & 0x7F) - 0x80
# twos complement subtraction
result1 = a1 - m1 - self.carry_flag
result1 = a1 - m1 - [1, 0][self.carry_flag]
# unsigned subtraction
result2 = a2 - m2 - self.carry_flag
result2 = a2 - m2 - [1, 0][self.carry_flag]
self.accumulator = self.update_nz(result2)
self.carry_flag = (result2 >= 0)