Class: GBRb::CPU::Rr

Inherits:
Instruction show all
Defined in:
lib/gbrb/cpu/instruction.rb

Instance Attribute Summary

Attributes inherited from Instruction

#i, #m, #t

Instance Method Summary collapse

Methods inherited from Instruction

#carry?, #immediate_count

Constructor Details

#initialize(target, carry = false, indirect = false, m = 2, t = 8) ⇒ Rr

Returns a new instance of Rr.



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# File 'lib/gbrb/cpu/instruction.rb', line 276

def initialize target, carry=false, indirect=false, m=2, t=8
  super m, t
  @target = target.to_sym
  @carry = carry
  @indirect = indirect
end

Instance Method Details

#call(r, mem) ⇒ Object 



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# File 'lib/gbrb/cpu/instruction.rb', line 283

def call r, mem
  if @indirect
    address = r.public_send(@target).read
    v = mem.read_byte(address)
  else
    v = r.public_send(@target).read
  end

  carry_out = v & 0x01

  carry_in = if @carry
               carry_out
             else
               r.carry_flag? ? 1 : 0
             end

  v >>= 1

  v += carry_in << 7

  if @indirect
    original = mem.read_byte address
    mem.write_byte(address, v)
  else
    r.public_send(@target).store v
  end

  r.clear_add_sub_flag
  r.clear_half_carry_flag
  v & 0xff == 0 ? r.set_zero_flag : r.clear_zero_flag
  carry_out == 1 ? r.set_carry_flag : r.clear_carry_flag
end