7.4.2.1 SPI Read and Write Transactions

Each SPI transaction to a single device is 17 bits long and is framed by SS_N when asserted low. The MOSI input is ignored, and the MISO output is floated whenever SS_N is deasserted (high).

The bits are shifted in left-to-right. The first bit is R/W, which is 1'b for read and 0'b for write. Bits A7-A0 are the 8-bit register address, and bits D7-D0 are the 8-bit read or write data. The previous SPI command, address, and data are shifted out on MISO as the current command, address, and data are shifted in on MOSI. In all SPI transactions, the MISO output signal is enabled asynchronously when SS_N asserts low. The contents of a single MOSI or MISO transaction frame are shown in Figure 14.