DM9000_NSR
int tx_status = ior(db, DM9000_NSR); /* Got TX status */
nsr = ior(db, DM9000_NSR);
iow(db, DM9000_NSR, NSR_WAKEST);
ret = dm9000_read_locked(dm, DM9000_NSR) & NSR_LINKST ? 1 : 0;
unsigned nsr = dm9000_read_locked(db, DM9000_NSR);
iow(db, DM9000_NSR, NSR_WAKEST | NSR_TX2END | NSR_TX1END);