Apple-2-Tools/applepy
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refactored flags to status byte and back

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This commit is contained in:
James Tauber 2011-08-06 21:12:02 -04:00
parent 20457db088
commit d6875b2419
1 changed files with 19 additions and 23 deletions
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42
applepy.py
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@ -311,6 +311,20 @@ class CPU:
####
def status_from_byte(self, status):
self.carry_flag = 0 != status & 1
self.zero_flag = 0 != status & 2
self.interrupt_disable_flag = 0 != status & 4
self.decimal_mode_flag = 0 != status & 8
self.break_flag = 0 != status & 16
self.overflow_flag = 0 != status & 64
self.sign_flag = 0 != status & 128
def status_as_byte(self):
return self.carry_flag | self.zero_flag << 1 | self.interrupt_disable_flag << 2 | self.decimal_mode_flag << 3 | self.break_flag << 4 | 1 << 5 | self.overflow_flag << 6 | self.sign_flag << 7
####
def immediate_mode(self):
return self.get_pc()
@ -541,8 +555,7 @@ class CPU:
self.memory.write_byte(s, self.accumulator)
def PHP(self):
status = self.carry_flag | self.zero_flag << 1 | self.interrupt_disable_flag << 2 | self.decimal_mode_flag << 3 | self.break_flag << 4 | 1 << 5 | self.overflow_flag << 6 | self.sign_flag << 7
status = self.status_as_byte()
s = self.STACK_PAGE + self.stack_pointer
self.stack_pointer = (self.stack_pointer - 1) % 0x100
self.memory.write_byte(s, status)
@ -553,15 +566,7 @@ class CPU:
def PLP(self):
self.stack_pointer = (self.stack_pointer + 1) % 0x100
s = self.STACK_PAGE + self.stack_pointer
status = self.memory.read_byte(s)
self.carry_flag = 0 != status & 1
self.zero_flag = 0 != status & 2
self.interrupt_disable_flag = 0 != status & 4
self.decimal_mode_flag = 0 != status & 8
self.break_flag = 0 != status & 16
self.overflow_flag = 0 != status & 64
self.sign_flag = 0 != status & 128
self.status_from_byte(self.memory.read_byte(self.STACK_PAGE + self.stack_pointer))
# LOGIC
@ -644,8 +649,8 @@ class CPU:
self.memory.write_byte(s, pc_lo)
# PHP
status = self.carry_flag | self.zero_flag << 1 | self.interrupt_disable_flag << 2 | self.decimal_mode_flag << 3 | self.break_flag << 4 | 1 << 5 | self.overflow_flag << 6 | self.sign_flag << 7
status = self.status_as_byte()
s = self.STACK_PAGE + self.stack_pointer
self.stack_pointer = (self.stack_pointer - 1) % 0x100
self.memory.write_byte(s, status)
@ -654,17 +659,8 @@ class CPU:
def RTI(self):
# PLP
self.stack_pointer = (self.stack_pointer + 1) % 0x100
s = self.STACK_PAGE + self.stack_pointer
status = self.memory.read_byte(s)
self.carry_flag = 0 != status & 1
self.zero_flag = 0 != status & 2
self.interrupt_disable_flag = 0 != status & 4
self.decimal_mode_flag = 0 != status & 8
self.break_flag = 0 != status & 16
self.overflow_flag = 0 != status & 64
self.sign_flag = 0 != status & 128
self.status_from_byte(self.memory.read_byte(self.STACK_PAGE + self.stack_pointer))
# pull PC
s = self.STACK_PAGE + self.stack_pointer + 1