BKTR_DSTATUS
c_temp = INB(bktr, BKTR_DSTATUS);
OUTB(bktr, BKTR_DSTATUS, 0);
dstatus = INB(bktr, BKTR_DSTATUS);
OUTB(bktr, BKTR_DSTATUS, 0x00);
OUTB(bktr, BKTR_DSTATUS, 0x00); /* clear device status reg. */