ML51Dec. 05, 2018 Page 254 of 401 Rev 1.00ML51 SERIES TECHNICAL REFERENCE MANUAL18.1.6 Slave modeSlave ReceiverIn the slave receiver mode, several bytes of data are received form a master transmitter. Before atransmission is commenced, I2CnADDRx should be loaded with the address to which the device willrespond when addressed by a master. I2CnCLK does not affect in slave mode. The AA bit should beset to enable acknowledging its own slave address. After the initialization above, the I2C idles until it isaddressed by its own address with the data direction bit “write” (SLA+W). The slave receiver modemay also be entered if arbitration is lost.After the slave is addressed by SLA+W, it should clear its SI flag to receive the data from the mastertransmitter. If the AA bit is 0 during a transaction, the slave will return a non-acknowledge after thenext received data byte. The slave will also become not addressed and isolate with the master. Itcannot receive any byte of data with I2CnDAT remaining the previous byte of data, which is justreceived.Slave TransmitterThe I2C port is equipped with four slave address registers, I2CnADDRx (x=0~3). The contents of theregister are irrelevant when I2C is in Master mode. In the slave transmitter mode, several bytes of dataare transmitted to a master receiver. After I2CnADDRx and I2CnCON values are given, the I2C waituntil it is addressed by its own address with the data direction bit “read” (SLA+R). The slavetransmitter mode may also be entered if arbitration is lost.After the slave is addressed by SLA+R, it should clear its SI flag to transmit the data to the masterreceiver. Normally the master receiver will return an acknowledge after every bytes of data istransmitted by the slave. If the acknowledge is not received, it will transmit all “1” data if it continuesthe transaction. It becomes a not addressed slave. If the AA flag is cleared during a transaction, theslave transmits the last byte of data. The next transmitting data will be all “1” and the slave becomesnot addressed.
