TWI_SR_RXRDY
if (sc->sc_flags & I2C_READING && sr & TWI_SR_RXRDY) {
if (isr & TWI_SR_RXRDY) {
if (isr & (TWI_SR_TXRDY | TWI_SR_RXRDY) && sc->sc_resid <= 0) {
at91twi_writereg(sc, TWI_IDR, TWI_SR_RXRDY | TWI_SR_TXRDY);
| (rd ? TWI_SR_RXRDY : TWI_SR_TXRDY));