FDCREG_SECTOR
FDC_WRITE( FDCREG_SECTOR, read_track ? 1 : ReqSector );
!(read_track && FDC_READ(FDCREG_SECTOR) > SUDT->spt)) {
SelectedDrive, FDC_READ (FDCREG_SECTOR), ReqSide, ReqTrack );
SelectedDrive, ReqSide, ReqTrack, FDC_READ (FDCREG_SECTOR) );
SelectedDrive, ReqSide, ReqTrack, FDC_READ (FDCREG_SECTOR) );