Class: Amaterasu::GameBoy::Cpu::Instructions::And

Inherits:
Base
  • Object
show all
Defined in:
lib/amaterasu/game_boy/cpu/instructions/and.rb,
sig/akane/game_boy/cpu/instructions/and.rbs

Overview

Handles the logic related to all possible AND instructions

  • AND A, r8
  • AND A, [HL]
  • AND A, n8

Instance Attribute Summary

Attributes inherited from Base

#mnemonic

Instance Method Summary collapse

Methods inherited from Base

#execute, #format_operand

Constructor Details

#initialize(cpu:, source:) ⇒ And 



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# File 'lib/amaterasu/game_boy/cpu/instructions/and.rb', line 15

def initialize(cpu:, source:)
  super(cpu:)

  @mnemonic = "AND A, #{source}"
  @logic    = build_logic(source)
end

Instance Method Details

#and_a(value) ⇒ void

This method returns an undefined value.

Performs a bitwise AND between a given value and the register A.

  • Sets the Zero flag if the result is zero, otherwise clears it.
  • Always clears the Subtraction flag.
  • Always sets the Half Carry flag.
  • Always clears the Carry flag.


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# File 'lib/amaterasu/game_boy/cpu/instructions/and.rb', line 48

def and_a(value)
  result = @registers.a & value

  @registers.z_flag = result.nobits?(0xFF)
  @registers.n_flag = false
  @registers.h_flag = true
  @registers.c_flag = false

  @registers.a = result
end

#build_logic(source) ⇒ Proc

Builds the logic for all AND instructions. Returns a lambda object to be called by the CPU.



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# File 'lib/amaterasu/game_boy/cpu/instructions/and.rb', line 26

def build_logic(source)
  case source
  when :a      then -> { and_a(@registers.a) }
  when :b      then -> { and_a(@registers.b) }
  when :c      then -> { and_a(@registers.c) }
  when :d      then -> { and_a(@registers.d) }
  when :e      then -> { and_a(@registers.e) }
  when :h      then -> { and_a(@registers.h) }
  when :l      then -> { and_a(@registers.l) }
  when :mem_hl then -> { and_a(@cpu.bus_read(address: @registers.hl)) }
  when :imm8   then -> { and_a(@cpu.fetch_next_byte) }
  else
    raise ArgumentError, 'Unknown And source'
  end
end