SPRUIU1C July 2020 – February 2024 DRA821U , DRA821U-Q1
The Private Write message transmitted over I3C bus in all supported transmit modes is presented in Figure 12-185, Master Write Transaction for Single and Multi Address Sequences. The provided transmit modes use additional I3C write frame that utilizes the data field to pass slave register address ahead of payload byte(s). As writing command word triggers start condition immediately, it shall be guaranteed by firmware that the data payload is written to the Tx FIFO in advance before it is going to be transmitted.
The completion of the message frame on the I3C bus is signaled by the I3C_MST_ISR[16] IMM_COMP interrupt.
In case of transfers with data payload greater than the TX FIFO size, firmware can use I3C_MST_ISR[15] TX_THR interrupt to fill the FIFO on time. The system design should prevent the TX FIFO from underflow. During the time elapsed between reading the last four bytes from almost empty TX FIFO and reading the subsequent one, firmware is required to refill the TX FIFO.