24.4.3.1.1 Read Register

Adding Register mode to Sensor mode allows SSI to evolve into BiSS. Register mode allows control of the reading and writing of registers by “saving” multiple CDS and CDM bits from multiple BiSS frames and combining them to form a full control frame. Therefore, Register mode always includes Sensor mode. There are different ways to use Register mode, such as reading and writing to registers and sending commands (see Initiating a Register Read).

Figure 24-8. Register Read
Note:
  1. The Control Select bit (CTS) is one (CTS =1) for the register communication.
  2. The secondary register access has only three ID select bits and seven bits of register address.
  3. * A Stop bit (P = 0) is at the end of the frame. Following the Stop bit, there can be an optional Start bit if the main must perform a sequential access of additional secondary registers.
  4. After the Start bit, the main sends 12 0 bits and one Stop bit. The secondary responds with eight bits of data protected with four bits of CRC.