SPRUJF2A March 2026 – March 2026 AM13E23019
Standard 7-bit addressing I2C data transfers follow the format shown in Figure 24-6. To transmit/receive using a 7-bit addressing mode, set TA.MODE=0 for UNICOMM-I2CC devices and OAR.MODE=0 for UNICOMM-I2CT devices.
The I2C controller initiates the START condition, then a target address is transmitted. This address is 7-bits long, followed by an eighth bit, which is a data direction bit, set by TA.DIR for UNICOMM-I2CC modules. A TA.DIR bit set to '0' indicates a transmit operation (send) a TA.DIR bit set to '1' indicates a request to receive data (receive). A data transfer is always terminated by a STOP condition generated by the controller. However, a controller can initiate communications with another device on the bus by generating a Repeated START condition and addressing another target without first generating a STOP condition, see section Figure 24-8. Various combinations of receive/transmit formats are then possible within a single transfer. The ninth bit is the Acknowledge bit, which is described in Section 24.2.3.7 .
The target address sent in the I2C frame matches the unique target address of a target device on the bus. For UNICOMM-I2CT devices, this unique address is programmed in the OAR.OAR register field, where the top 3 bits are "don't care" in for 7-bit addressing mode. If the UNICOMM-I2CT device receives an address byte on the bus matching the address programmed in OAR.OAR with a read bit, it shifts the data bytes that follow into the RX FIFO. If the UNICOMM-I2CT device receives an address byte on the bus matching the address programmed in OAR.OAR with a write bit, it shifts out the data bytes in the TX FIFO and onto the SDA line.
Figure 24-6 Data Format with 7-Bit Address