mf_rsr
rsr = MFP->mf_rsr;
if ((rsr & RSR_BREAK) && (MFP->mf_rsr & RSR_BREAK))
rsr = MFP->mf_rsr;
rsr = MFP->mf_rsr;
MFP->mf_rsr = RSR_ENAB;
while (!ISSET(stat = MFP->mf_rsr, RSR_BFULL)) {
MFP->mf_rsr |= RSR_ENAB;
while (ISSET(MFP->mf_rsr, RSR_CIP|RSR_BFULL))
MFP->mf_rsr = sc->sc_rsr;