GameBoy\Core::performHdma PHP Method

    public function performHdma()
    {
        $this->CPUTicks += 1 + 8 * $this->multiplier;
        $dmaSrc = ($this->memory[0xff51] << 8) + $this->memory[0xff52];
        $dmaDstRelative = ($this->memory[0xff53] << 8) + $this->memory[0xff54];
        $dmaDstFinal = $dmaDstRelative + 0x10;
        $tileRelative = $this->tileData->length - $this->tileCount;
        if ($this->currVRAMBank == 1) {
            while ($dmaDstRelative < $dmaDstFinal) {
                // Bkg Tile data area
                if ($dmaDstRelative < 0x1800) {
                    $tileIndex = ($dmaDstRelative >> 4) + 384;
                    if ($this->tileReadState[$tileIndex] == 1) {
                        $r = $tileRelative + $tileIndex;
                        do {
                            $this->tileData[$r] = null;
                            $r -= $this->tileCount;
                        } while ($r >= 0);
                        $this->tileReadState[$tileIndex] = 0;
                    }
                }
                $this->VRAM[$dmaDstRelative++] = $this->memoryRead($dmaSrc++);
            }
        } else {
            while ($dmaDstRelative < $dmaDstFinal) {
                // Bkg Tile data area
                if ($dmaDstRelative < 0x1800) {
                    $tileIndex = $dmaDstRelative >> 4;
                    if ($this->tileReadState[$tileIndex] == 1) {
                        $r = $tileRelative + $tileIndex;
                        do {
                            $this->tileData[$r] = null;
                            $r -= $this->tileCount;
                        } while ($r >= 0);
                        $this->tileReadState[$tileIndex] = 0;
                    }
                }
                $this->memory[0x8000 + $dmaDstRelative++] = $this->memoryRead($dmaSrc++);
            }
        }
        $this->memory[0xff51] = ($dmaSrc & 0xff00) >> 8;
        $this->memory[0xff52] = $dmaSrc & 0xf0;
        $this->memory[0xff53] = ($dmaDstFinal & 0x1f00) >> 8;
        $this->memory[0xff54] = $dmaDstFinal & 0xf0;
        if ($this->memory[0xff55] == 0) {
            $this->hdmaRunning = false;
            $this->memory[0xff55] = 0xff;
            //Transfer completed ("Hidden last step," since some ROMs don't imply this, but most do).
        } else {
            --$this->memory[0xff55];
        }
    }