SWCU193A April 2023 – August 2024 CC2340R2 , CC2340R5 , CC2340R5-Q1
Data transfers follow the format shown in Figure 21-4. After the Start condition, a target address is transmitted. This address is 7 bits long followed by an eighth bit, which is a data direction bit (the RS bit in the I2C:CSA register). If the RS bit is clear, the operation is a transmit (send), and if the RS bit is set, the operation is a request for 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. Various combinations of receive and transmit formats are then possible within a single transfer.
The first 7 bits of the first byte comprise the target address (see Figure 21-5). The eighth bit determines the direction of the message. A 0 in the R/S position of the first byte means that the controller transmits (sends) data to the selected target, and a 1 in this position means that the controller receives data from the target.