Fixed that ADC would not properly set the V flag. Closes #3.

CHANGES.txt

@@ -4,6 +4,13 @@ Next Release
 
   - Fixed that ASL would not properly set the Z flag.  Closes #7.
 
+  - Fixed that ADC would not properly set the Overflow (V) flag.  The
+    overflow calculation that is now used originated from XGS: Apple
+    IIGS Emulator (cputable.h).  Originally written and Copyright 
+    (C)1996 by Joshua M. Thompson.  Copyright (C) 2006 by Samuel A. 
+    Falvo II.  http://bitbucket.org/kc5tja/lib65816/src/tip/src/cputable.h
+    Closes #3.
+
 0.5 (2009-08-06)
 
   - Fixed signatures of getc/putc callbacks in monitor that were broken

src/py65/devices/mpu6502.py

@@ -296,8 +296,11 @@ class MPU:
         tmp = 1
       else:
         tmp = 0
-      data += self.a + tmp
+      result = data + self.a + tmp
       self.flags &= ~(self.CARRY+self.OVERFLOW+self.NEGATIVE+self.ZERO)
+      if ( ~(self.a ^ data) & (self.a ^ result) ) & 0x80:
+        self.flags |= self.OVERFLOW
+      data = result
       if data > 255:
         self.flags|=self.OVERFLOW+self.CARRY
         data &=255

src/py65/tests/devices/test_mpu6502.py

@@ -71,6 +71,19 @@ class Common6502Tests:
     self.assertEquals(mpu.OVERFLOW, mpu.flags & mpu.OVERFLOW)       
     self.assertEquals(0, mpu.flags & mpu.ZERO)       
 
+  def test_adc_bcd_off_absolute_overflow_set_on_40_plus_40(self):
+    mpu = self._make_mpu()
+    mpu.flags &= ~(mpu.OVERFLOW)
+    mpu.a = 0x40
+    self._write(mpu.memory, 0x0000, (0x6D, 0x00, 0xC0)) #=> $0000 ADC $C000
+    mpu.memory[0xC000] = 0x40
+    mpu.step()
+    self.assertEquals(0x0003, mpu.pc)
+    self.assertEquals(0x80, mpu.a)
+    self.assertEquals(mpu.NEGATIVE, mpu.flags & mpu.NEGATIVE)    
+    self.assertEquals(mpu.OVERFLOW, mpu.flags & mpu.OVERFLOW)       
+    self.assertEquals(0, mpu.flags & mpu.ZERO)       
+
   # ADC Zero Page
   
   def test_adc_bcd_off_zp_carry_clear_in_accumulator_zeroes(self):
@@ -133,6 +146,19 @@ class Common6502Tests:
     self.assertEquals(mpu.NEGATIVE, mpu.flags & mpu.NEGATIVE)    
     self.assertEquals(mpu.OVERFLOW, mpu.flags & mpu.OVERFLOW)       
     self.assertEquals(0, mpu.flags & mpu.ZERO)       
+
+  def test_adc_bcd_off_zp_overflow_set_on_40_plus_40(self):
+    mpu = self._make_mpu()
+    mpu.a = 0x40
+    mpu.flags &= ~(mpu.OVERFLOW)
+    self._write(mpu.memory, 0x0000, (0x65, 0xB0)) #=> $0000 ADC $00B0
+    mpu.memory[0x00B0] = 0x40
+    mpu.step()
+    self.assertEquals(0x0002, mpu.pc)
+    self.assertEquals(0x80, mpu.a)
+    self.assertEquals(mpu.NEGATIVE, mpu.flags & mpu.NEGATIVE)    
+    self.assertEquals(mpu.OVERFLOW, mpu.flags & mpu.OVERFLOW)       
+    self.assertEquals(0, mpu.flags & mpu.ZERO)       
       
   # ADC Immediate
   
@@ -192,6 +218,17 @@ class Common6502Tests:
     self.assertEquals(mpu.OVERFLOW, mpu.flags & mpu.OVERFLOW)       
     self.assertEquals(0, mpu.flags & mpu.ZERO)       
 
+  def test_adc_bcd_off_immediate_overflow_set_on_40_plus_40(self):
+    mpu = self._make_mpu()
+    mpu.a = 0x40
+    self._write(mpu.memory, 0x0000, (0x69, 0x40)) #=> $0000 ADC #$40
+    mpu.step()
+    self.assertEquals(0x0002, mpu.pc)
+    self.assertEquals(0x80, mpu.a)
+    self.assertEquals(mpu.NEGATIVE, mpu.flags & mpu.NEGATIVE)    
+    self.assertEquals(mpu.OVERFLOW, mpu.flags & mpu.OVERFLOW)       
+    self.assertEquals(0, mpu.flags & mpu.ZERO)       
+
   # ADC Absolute, X-Indexed
   
   def test_adc_bcd_off_abs_x_carry_clear_in_accumulator_zeroes(self):
@@ -260,6 +297,20 @@ class Common6502Tests:
     self.assertEquals(mpu.OVERFLOW, mpu.flags & mpu.OVERFLOW)       
     self.assertEquals(0, mpu.flags & mpu.ZERO)       
 
+  def test_adc_bcd_off_abs_x_overflow_set_on_40_plus_40(self):
+    mpu = self._make_mpu()
+    mpu.flags &= ~(mpu.OVERFLOW)
+    mpu.a = 0x40
+    mpu.x = 0x03
+    self._write(mpu.memory, 0x0000, (0x7D, 0x00, 0xC0)) #=> $0000 ADC $C000,X
+    mpu.memory[0xC000 + mpu.x] = 0x40
+    mpu.step()
+    self.assertEquals(0x0003, mpu.pc)
+    self.assertEquals(0x80, mpu.a)
+    self.assertEquals(mpu.NEGATIVE, mpu.flags & mpu.NEGATIVE)    
+    self.assertEquals(mpu.OVERFLOW, mpu.flags & mpu.OVERFLOW)       
+    self.assertEquals(0, mpu.flags & mpu.ZERO)       
+
   # ADC Absolute, Y-Indexed
   
   def test_adc_bcd_off_abs_y_carry_clear_in_accumulator_zeroes(self):
@@ -328,6 +379,20 @@ class Common6502Tests:
     self.assertEquals(mpu.OVERFLOW, mpu.flags & mpu.OVERFLOW)       
     self.assertEquals(0, mpu.flags & mpu.ZERO)       
 
+  def test_adc_bcd_off_abs_y_overflow_set_on_40_plus_40(self):
+    mpu = self._make_mpu()
+    mpu.flags &= ~(mpu.OVERFLOW)
+    mpu.a = 0x40
+    mpu.y = 0x03
+    self._write(mpu.memory, 0x0000, (0x79, 0x00, 0xC0)) #=> $0000 ADC $C000,Y
+    mpu.memory[0xC000 + mpu.y] = 0x40
+    mpu.step()
+    self.assertEquals(0x0003, mpu.pc)
+    self.assertEquals(0x80, mpu.a)
+    self.assertEquals(mpu.NEGATIVE, mpu.flags & mpu.NEGATIVE)    
+    self.assertEquals(mpu.OVERFLOW, mpu.flags & mpu.OVERFLOW)       
+    self.assertEquals(0, mpu.flags & mpu.ZERO)       
+
   # ADC Zero Page, X-Indexed
   
   def test_adc_bcd_off_zp_x_carry_clear_in_accumulator_zeroes(self):
@@ -396,6 +461,20 @@ class Common6502Tests:
     self.assertEquals(mpu.OVERFLOW, mpu.flags & mpu.OVERFLOW)       
     self.assertEquals(0, mpu.flags & mpu.ZERO)       
 
+  def test_adc_bcd_off_zp_x_overflow_set_on_40_plus_40(self):
+    mpu = self._make_mpu()
+    mpu.flags &= ~(mpu.OVERFLOW)
+    mpu.a = 0x40
+    mpu.x = 0x03
+    self._write(mpu.memory, 0x0000, (0x75, 0x10)) #=> $0000 ADC $0010,X
+    mpu.memory[0x0010 + mpu.x] = 0x40
+    mpu.step()
+    self.assertEquals(0x0002, mpu.pc)
+    self.assertEquals(0x80, mpu.a)
+    self.assertEquals(mpu.NEGATIVE, mpu.flags & mpu.NEGATIVE)    
+    self.assertEquals(mpu.OVERFLOW, mpu.flags & mpu.OVERFLOW)       
+    self.assertEquals(0, mpu.flags & mpu.ZERO)       
+
   # ADC Indirect, Indexed (X)
   
   def test_adc_bcd_off_indirect_indexed_carry_clear_in_accumulator_zeroes(self):
@@ -469,6 +548,21 @@ class Common6502Tests:
     self.assertEquals(mpu.OVERFLOW, mpu.flags & mpu.OVERFLOW)       
     self.assertEquals(0, mpu.flags & mpu.ZERO)       
 
+  def test_adc_bcd_off_indirect_indexed_overflow_set_on_40_plus_40(self):
+    mpu = self._make_mpu()
+    mpu.flags &= ~(mpu.OVERFLOW)
+    mpu.a = 0x40
+    mpu.x = 0x03
+    self._write(mpu.memory, 0x0000, (0x61, 0x10)) #=> $0000 ADC ($0010,X)
+    self._write(mpu.memory, 0x0013, (0xCD, 0xAB)) #=> Vector to $ABCD
+    mpu.memory[0xABCD] = 0x40
+    mpu.step()
+    self.assertEquals(0x0002, mpu.pc)
+    self.assertEquals(0x80, mpu.a)
+    self.assertEquals(mpu.NEGATIVE, mpu.flags & mpu.NEGATIVE)    
+    self.assertEquals(mpu.OVERFLOW, mpu.flags & mpu.OVERFLOW)       
+    self.assertEquals(0, mpu.flags & mpu.ZERO)       
+
   # ADC Indexed, Indirect (Y)
 
   def test_adc_bcd_off_indexed_indirect_carry_clear_in_accumulator_zeroes(self):
@@ -531,10 +625,10 @@ class Common6502Tests:
   def test_adc_bcd_off_indexed_indirect_indexed_overflow(self):
     mpu = self._make_mpu()
     mpu.a = 0xFF
-    mpu.x = 0x03
+    mpu.y = 0x03
-    self._write(mpu.memory, 0x0000, (0x61, 0x10)) #=> $0000 ADC ($0010,X)
+    self._write(mpu.memory, 0x0000, (0x71, 0x10)) #=> $0000 ADC ($0010),Y
-    self._write(mpu.memory, 0x0013, (0xCD, 0xAB)) #=> Vector to $ABCD
+    self._write(mpu.memory, 0x0010, (0xCD, 0xAB)) #=> Vector to $ABCD
-    mpu.memory[0xABCD] = 0xFF
+    mpu.memory[0xABCD + mpu.y] = 0xFF
     mpu.step()
     self.assertEquals(0x0002, mpu.pc)
     self.assertEquals(0xFE, mpu.a)
@@ -542,6 +636,21 @@ class Common6502Tests:
     self.assertEquals(mpu.OVERFLOW, mpu.flags & mpu.OVERFLOW)       
     self.assertEquals(0, mpu.flags & mpu.ZERO)       
 
+  def test_adc_bcd_off_indexed_indirect_overflow_set_on_40_plus_40(self):
+    mpu = self._make_mpu()
+    mpu.flags &= ~(mpu.OVERFLOW)
+    mpu.a = 0x40
+    mpu.y = 0x03
+    self._write(mpu.memory, 0x0000, (0x71, 0x10)) #=> $0000 ADC ($0010),Y
+    self._write(mpu.memory, 0x0010, (0xCD, 0xAB)) #=> Vector to $ABCD
+    mpu.memory[0xABCD + mpu.y] = 0x40
+    mpu.step()
+    self.assertEquals(0x0002, mpu.pc)
+    self.assertEquals(0x80, mpu.a)
+    self.assertEquals(mpu.NEGATIVE, mpu.flags & mpu.NEGATIVE)    
+    self.assertEquals(mpu.OVERFLOW, mpu.flags & mpu.OVERFLOW)       
+    self.assertEquals(0, mpu.flags & mpu.ZERO)       
+
   # AND (Absolute)
   
   def test_and_absolute_all_zeros_setting_zero_flag(self):