     return;
   }
 
+  // Sound Register
+  if (
+    (address >= 0xFF10 and address <= 0xFF14) or
+    (address >= 0xFF16 and address <= 0xFF1E) or
+    (address >= 0xFF20 and address <= 0xFF26) or
+    (address >= 0xFF30 and address <= 0xFF3F)
+  ) {
+    return sound_write(address, value);
+  }
+
+  // GPU Register
   if (address & 0xF0) >= 0x40 and (address & 0xF0) <= 0x70 {
-    // GPU Register
     return gpu_write(address, value);
+  }
+
+  // SB – Serial Transfer Data (R/W)
+  // SC – Serial Transfer Control (R/W)
+  if (address == 0xFF01 or address == 0xFF02) {
+    // TODO: Implement link cable / debug printout
+    return;
   }
 
   // IF – Interrupt Flag (R/W)

  // won't execute properly without MBC1 support, but the individual
  // Roms will work fine.

  // open_rom("/Users/mehcode/Workspace/gb-test-roms/cpu_instrs/individual/01-special.gb");
  // open_rom("/Users/mehcode/Workspace/gb-test-roms/cpu_instrs/individual/02-interrupts.gb");

  // PASS

    y += 1;
  }

  SDL_RenderPresent(_renderer);
}

