RL_ISR
status = CSR_READ_2(sc, RL_ISR);
CSR_WRITE_2(sc, RL_ISR, status);
CSR_WRITE_2(sc, RL_ISR, sc->rl_intrs);
CSR_WRITE_2(sc, RL_ISR, 0xFFFF);
status = CSR_READ_2(sc, RL_ISR);
CSR_WRITE_2(sc, RL_ISR, status);