Apple-2-Tools/applepy
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refactored addressing mode code

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This commit is contained in:
James Tauber 2011-08-06 18:07:50 -04:00
parent a48716a900
commit fef234f7c0
1 changed files with 20 additions and 19 deletions
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39
applepy.py
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@ -299,15 +299,24 @@ class CPU:
#### ####
def get_pc(self, inc=1):
pc = self.program_counter
self.program_counter += inc
return pc
def read_pc_byte(self):
return self.memory.read_byte(self.get_pc())
def read_pc_word(self):
return self.memory.read_word(self.get_pc(2))
####
def immediate_mode(self): def immediate_mode(self):
address = self.program_counter return self.get_pc()
self.program_counter += 1
return address
def absolute_mode(self): def absolute_mode(self):
address = self.memory.read_word(self.program_counter) return self.read_pc_word()
self.program_counter += 2
return address
def absolute_x_mode(self): def absolute_x_mode(self):
return self.absolute_mode() + signed(self.x_index) return self.absolute_mode() + signed(self.x_index)
@ -316,9 +325,7 @@ class CPU:
return self.absolute_mode() + signed(self.y_index) return self.absolute_mode() + signed(self.y_index)
def zero_page_mode(self): def zero_page_mode(self):
address = self.memory.read_byte(self.program_counter) return self.read_pc_byte()
self.program_counter += 1
return address
def zero_page_x_mode(self): def zero_page_x_mode(self):
return self.zero_page_mode() + signed(self.x_index) return self.zero_page_mode() + signed(self.x_index)
@ -327,20 +334,14 @@ class CPU:
return self.memory.read_word(self.absolute_mode()) return self.memory.read_word(self.absolute_mode())
def indirect_x_mode(self): def indirect_x_mode(self):
address = self.memory.read_word((self.memory.read_byte(self.program_counter) + signed(self.x_index)) % 0x100) return self.memory.read_word((self.read_pc_byte() + signed(self.x_index)) % 0x100)
self.program_counter += 1
return address
def indirect_y_mode(self): def indirect_y_mode(self):
address = self.memory.read_word(self.memory.read_byte(self.program_counter)) + signed(self.y_index) return self.memory.read_word(self.read_pc_byte()) + signed(self.y_index)
self.program_counter += 1
return address
def relative_mode(self): def relative_mode(self):
pc = self.program_counter pc = self.get_pc()
self.program_counter += 1 return pc + 1 + signed(self.memory.read_byte(pc))
address = pc + 1 + signed(self.memory.read_byte(pc))
return address
#### ####