GameBoy\Core::unsbtub PHP Метод

    public function unsbtub($ubyte)
    {
        //Keep an unsigned byte unsigned:
        if ($ubyte < 0) {
            $ubyte += 0x100;
        }
        return $ubyte;
        //If this function is called, no wrapping requested.
    }

 /**
  * Opcode #0xFE.
  *
  * CP n
  *
  * @param Core $core
  */
 public static function opcode254(Core $core)
 {
     $dirtySum = $core->registerA - $core->memoryRead($core->programCounter);
     $core->FHalfCarry = ($core->unsbtub($dirtySum) & 0xf) > ($core->registerA & 0xf);
     $core->FCarry = $dirtySum < 0;
     $core->FZero = $dirtySum == 0;
     $core->programCounter = $core->programCounter + 1 & 0xffff;
     $core->FSubtract = true;
 }