public void MoveHeadIn()
{
if (current_halftrack == D64Drive.NUM_TRACKS * 2)
return;
current_halftrack++;
gcr_ptr = gcr_track_start = (UInt32)(((current_halftrack >> 1) - 1) * GCR_TRACK_SIZE);
gcr_track_end = (UInt32)(gcr_track_start + D64Drive.num_sectors[current_halftrack >> 1] * GCR_SECTOR_SIZE);
}