loop cpu forever, make cpu tick other components

src/crab/cpu.cr

@@ -59,6 +59,7 @@ class CPU
     else
       arm_execute instr
     end
+    @gba.tick 1
   end
 
   def check_cond(cond : Word) : Bool

src/crab/gba.cr

@@ -13,6 +13,8 @@ class GBA
   getter display : Display { Display.new }
   getter ppu : PPU { PPU.new self }
 
+  @cycles = 0
+
   def initialize(rom_path : String)
     @cartridge = Cartridge.new rom_path
 
@@ -34,13 +36,17 @@ class GBA
   end
 
   def run : Nil
-    # puts @cartridge.title
     loop do
-      280896.times do
-        cpu.tick
-      end
-      ppu.tick 280896
+      cpu.tick
+    end
+  end
+
+  def tick(cycles : Int) : Nil
+    ppu.tick cycles
+    @cycles += cycles
+    if @cycles >= PPU::REFRESH
       handle_events
+      @cycles -= PPU::REFRESH
     end
   end
 end

src/crab/ppu.cr

@@ -3,6 +3,14 @@ class PPU
   VRAM           = 0x06000000..0x06017FFF
   OAM            = 0x07000000..0x070003FF
 
+  # Display timings in cycles
+  HDRAW    = 960
+  HBLANK   = 272
+  SCANLINE = HDRAW + HBLANK
+  VDRAW    = 160 * SCANLINE
+  VBLANK   = 68 * SCANLINE
+  REFRESH  = VDRAW + VBLANK
+
   # LCD Control
   class DISPCNT < BitField(UInt16)
     bool obj_window_display
@@ -25,11 +33,17 @@ class PPU
 
   @dispcnt : DISPCNT = DISPCNT.new 0
 
+  @cycles = 0
+
   def initialize(@gba : GBA)
   end
 
   def tick(cycles : Int) : Nil
-    @gba.display.draw @vram
+    @cycles += cycles
+    if @cycles >= REFRESH
+      @gba.display.draw @vram
+      @cycles -= REFRESH
+    end
   end
 
   def [](index : Int) : Byte