documentation updats

lib/waterfoul/boot_rom.rb

@@ -51,7 +51,6 @@ module Waterfoul
 
 
     # Read bootstrap instruction given an index (memory location)
-    # @return Integer - instruction or immediate value
     def self.[](i)
       ROM[i]
     end

lib/waterfoul/cpu.rb

@@ -9,8 +9,8 @@ require 'waterfoul/instructions/shift'
 require 'waterfoul/instructions/prefix'
 
 module Waterfoul
-  # These constants represent each state in the F register and are used as a helper to
-  # reference the state when setting/resetting a state bit. Any combination of these
+  # These constants represent status bit in the F register. These are used as a
+  # helper when setting/resetting a state bit. Any combination of these
   # states can be set at any one time.
   #
   # Z_FLAG: Zero Flag
@@ -18,25 +18,20 @@ module Waterfoul
   # H_FLAG: half carry flag
   # C_FLAG: Carry Flag
   # BIT 0-3 Always 0 and not used
-  #
   Z_FLAG = 0b1000_0000
   N_FLAG = 0b0100_0000
   H_FLAG = 0b0010_0000
   C_FLAG = 0b0001_0000
 
-  # number of cycles a HALT will puase program execution for
-  HALT_CYCLES = 6
-
-  ##
-  # The CPU emulates the Sharp LR35902 CPU that is built into the device, similar to the
-  # Intel 8080 and Zilog Z80 processor. Each instruction is categorized
-  # into a subset of instructions by the type of action performed by the instruction.
+  # The CPU emulates the Sharp LR35902 CPU that is built into the device,
+  # similar to the Intel 8080 and Zilog Z80 processor. Each instruction
+  # is categorized into a subset of instructions by the type of action
+  # performed by the instruction.
   #
-  # See lib/instuctions/ for the implementation for the CPU instruction set.
+  # See lib/instuctions for the implementation for the CPU instruction set.
   #
   # I recommend looking at http://www.pastraiser.com/cpu/gameboy/gameboy_opcodes.html for an
   # easy to understand chart for each instruction.
-  #
   class CPU
     include Helper
     include Instructions::Opcode
@@ -51,7 +46,7 @@ module Waterfoul
 
     # 8 bit registers
     attr_reader :a, :b, :c, :d, :e, :f, :h, :l, :f
-    # 8 CPU clock
+    # CPU cycle count
     attr_reader :m
     # 16 bit registers
     attr_reader :sp, :pc
@@ -89,7 +84,7 @@ module Waterfoul
     end
 
     def halted?
-      @halt == true
+      @halt
     end
 
     # Execute the instruction and
@@ -103,7 +98,7 @@ module Waterfoul
 
     # fetch the next byte to be executed from memory and increment the program
     # counter (except under particular circumstances, see interrupts)
-    def fetch_instruction(increment_pc = false)
+    def fetch_instruction(no_increment_pc = false)
       instruction_byte = $mmu.read_byte @pc
       @pc = (@pc + 1) & 0xFFFF unless increment_pc
       instruction_byte

lib/waterfoul/emulator.rb

@@ -1,22 +1,18 @@
-require 'sdl2'
-
 module Waterfoul
+  # The Emulator is the abstraction of the emulator as a whole, it initializes
+  # each component and performs the tick.
   class Emulator
     def initialize(rom_filename, options = {})
-      SDL2.init SDL2::INIT_EVERYTHING
-      # read the rom into host memory
-      rom = read_program(rom_filename).bytes
-      # initialize emulated CPU, GPU & Sound components
+      # read the given file as binary and break it down into an array of bytes
+      rom = File.binread(rom_filename).bytes
+      # initialize emulated CPU, GPU & Scren components
       cartridge = Cartridge.new rom
-      # initialize emulated memory management unit
       $mmu = MMU.new
-      $mmu.cartridge = cartridge
-      cpu = CPU.new
-      @cpu = options.has_key?('skip_boot') ? SkipBoot.set_state(cpu) : cpu
+      @cpu = CPU.new
+      @cpu = SkipBoot.set_state(@cpu) if options.has_key?('skip_boot')
       @gpu = GPU.new
       # @input = Input.new
       @screen = Screen.new
-      # @sound = Sound.new
     end
 
     def run
@@ -25,14 +21,7 @@ module Waterfoul
         @gpu.step @cpu.m
         @screen.render @gpu.framebuffer if @gpu.vblank?
         # @input.step @cpu.m
-        # @sound.step
       end
     end
-
-    private
-
-    def read_program(rom)
-      File.binread rom
-    end
   end
 end

lib/waterfoul/helper.rb

@@ -1,5 +1,6 @@
 module Waterfoul
   module Helper
+
     def pop_from_stack(word = true)
       if word
         lower = $mmu.read_byte @sp

lib/waterfoul/interrupt.rb

@@ -12,6 +12,7 @@ module Waterfoul
     INTERRUPT_SERIAL  = 0x8
     INTERRUPT_JOYPAD  = 0x10
 
+    #
     def self.request_interrupt(interrupt)
       if_reg = $mmu.read_byte IF_REG_MEM_LOC
       $mmu.write_byte IF_REG_MEM_LOC, (if_reg | interrupt)

lib/waterfoul/mmu.rb

@@ -7,12 +7,11 @@ module Waterfoul
   # does not implement any IO instructions.
   class MMU
     MEMORY_SIZE = 65536 # bytes
-    # location in memory that when written to will unmap the boot rom from
-    # memory
+    # unmap boot rom register address
     UNMAP_BOOT_ROM_MEM_LOC = 0xFF50
     # location in memory where the boot rom ends
     BOOT_ROM_END_MEM_LOC = 0xFF
-    # location in memory where DMA transfer is init
+    # DMA register function address
     DMA_TRANSFER_MEM_LOC = 0xFF46
     # DIV register memory location
     DIV_MEM_LOC = 0xFF04
@@ -23,19 +22,19 @@ module Waterfoul
     # Set the initial state the memory management unit when program starts
     def initialize
       @cartridge = []
-      # flag to indicate if the boot rom is mapped to memory
+      # map the boot rom by default
       @map_boot_rom = true
       # storage for usable memory (zero filled)
       @memory = Array.new MEMORY_SIZE, 0
     end
 
     # Read 1 byte from memory given address
-    # @param i Integer location in memory to read value
     def [](i)
       raise MemoryOutOfBounds if i > MEMORY_SIZE || i < 0
 
       case i
       when 0x0000...0x8000 # ROM Bank 0 + n
+        # if the boot rom is enabled and the address is < 0x100
         if @map_boot_rom && i <= BOOT_ROM_END_MEM_LOC
           BootROM[i]
         else
@@ -54,14 +53,12 @@ module Waterfoul
       end
     end
 
-    ##
-    # Storage 1 byte into memory given address
-    # @param i Integer location in memory to storage value
-    # @param v Integer value to be written into memory
+    # Write 1 byte into memory
     def []=(i, v, options = {})
       # raise exception if an attempt is made to read memory that is out of bounds
       raise MemoryOutOfBounds if i > MEMORY_SIZE || i < 0
-
+      # ignore memory rules if emulated hardware components need to write to
+      # memory
       unless options[:hardware_operation]
         case i
         when UNMAP_BOOT_ROM_MEM_LOC # unmap the boot rom when 0xFF50 is wrtiten to in memory

lib/waterfoul/skip_boot.rb

@@ -1,7 +1,10 @@
 module Waterfoul
-  # Set the state of the emulator after it has finished running the bootloader and ready to execute
-  # the game program. This lets us run the game program without needing to execute the boot rom every time
-  # the emulator is started.
+  # Set the state of the emulator as defined to the same state as it typically
+  # is after it has finished running the bootloader and ready to execute the
+  # game program.
+
+  # This lets us run the game without needing to execute the boot rom
+  # every time the emulator is started.
   class SkipBoot
     def self.set_state(cpu)
       # CPU registers