Module: Badline::InstructionSet::IncDec

Included in:
Badline::InstructionSet
Defined in:
lib/badline/instruction_set/inc_dec.rb

Instance Method Summary collapse

Instance Method Details

#dec(addr, value) ⇒ Object

Decrements memory location by one.

Opcodes:

$C6 - zeropage   - 5 cycles
$CE - absolute   - 6 cycles
$D6 - zeropage_x - 6 cycles
$DE - absolute_x - 7 cycles



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# File 'lib/badline/instruction_set/inc_dec.rb', line 13

def dec(addr, value)
  v = resolve(value)
  result = (v - 1) & 0xff
  write_modified(addr, v, result)
  update_number_flags(result)
end

#dex(_addr, _value) ⇒ Object

Decrements X register by one.

Opcodes:

$CA - implied - 2 cycles



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# File 'lib/badline/instruction_set/inc_dec.rb', line 24

def dex(_addr, _value)
  cycle { @x = (@x - 1) & 0xff }
  update_number_flags(@x)
end

#dey(_addr, _value) ⇒ Object

Decrements Y register by one.

Opcodes:

$88 - implied - 2 cycles



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# File 'lib/badline/instruction_set/inc_dec.rb', line 33

def dey(_addr, _value)
  cycle { @y = (@y - 1) & 0xff }
  update_number_flags(@y)
end

#inc(addr, value) ⇒ Object

Increments memory location by one.

Opcodes:

$E6 - zeropage   - 5 cycles
$EE - absolute   - 6 cycles
$F6 - zeropage_x - 6 cycles
$FE - absolute_x - 7 cycles



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# File 'lib/badline/instruction_set/inc_dec.rb', line 45

def inc(addr, value)
  v = resolve(value)
  result = (v + 1) & 0xff
  write_modified(addr, v, result)
  update_number_flags(result)
end

#inx(_addr, _value) ⇒ Object

Increments X register by one.

Opcodes:

$E8 - implied - 2 cycles



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# File 'lib/badline/instruction_set/inc_dec.rb', line 56

def inx(_addr, _value)
  cycle { @x = (@x + 1) & 0xff }
  update_number_flags(@x)
end

#iny(_addr, _value) ⇒ Object

Increments Y register by one.

Opcodes:

$C8 - implied - 2 cycles



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# File 'lib/badline/instruction_set/inc_dec.rb', line 65

def iny(_addr, _value)
  cycle { @y = (@y + 1) & 0xff }
  update_number_flags(@y)
end