Data Modes

There are four combinations of SCK phase and polarity with respect to serial data. The desired combination is selected by writing to the MODE bits in the Control B register (SPI.CTRLB).

The SPI data transfer formats are shown below. Data bits are shifted out and latched in on opposite edges of the SCK signal, ensuring sufficient time for data signals to stabilize.

The leading edge is the first clock edge of a clock cycle. The trailing edge is the last clock edge of a clock cycle.

Figure 1. SPI Data Transfer Modes