fixed inverse use of carry in SBC

2011-08-06 23:53:47 -04:00 · 2011-08-06 23:53:47 -04:00 · 8f10724a7f
parent 6e709fcc4c
commit 8f10724a7f
1 changed files with 2 additions and 2 deletions
--- a/applepy.py
+++ b/applepy.py
@ -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)