CPOL=BUS_LOW, CPHA=FIRST_CLOCK, FRF=SPI
Control Register 0. Selects the serial clock rate, bus type, and data size.
| DSS | Data Size Select. This field controls the number of bits transferred in each frame. Values 0000-0010 are not supported and should not be used. 3 (4_BIT_TRANSFER): 4-bit transfer 4 (5_BIT_TRANSFER): 5-bit transfer 5 (6_BIT_TRANSFER): 6-bit transfer 6 (7_BIT_TRANSFER): 7-bit transfer 7 (8_BIT_TRANSFER): 8-bit transfer 8 (9_BIT_TRANSFER): 9-bit transfer 9 (10_BIT_TRANSFER): 10-bit transfer 10 (11_BIT_TRANSFER): 11-bit transfer 11 (12_BIT_TRANSFER): 12-bit transfer 12 (13_BIT_TRANSFER): 13-bit transfer 13 (14_BIT_TRANSFER): 14-bit transfer 14 (15_BIT_TRANSFER): 15-bit transfer 15 (16_BIT_TRANSFER): 16-bit transfer |
| FRF | Frame Format. 0 (SPI): SPI 1 (TI): TI 2 (MICROWIRE): Microwire 3 (THIS_COMBINATION_IS_): This combination is not supported and should not be used. |
| CPOL | Clock Out Polarity. This bit is only used in SPI mode. 0 (BUS_LOW): SSP controller maintains the bus clock low between frames. 1 (BUS_HIGH): SSP controller maintains the bus clock high between frames. |
| CPHA | Clock Out Phase. This bit is only used in SPI mode. 0 (FIRST_CLOCK): SSP controller captures serial data on the first clock transition of the frame, that is, the transition away from the inter-frame state of the clock line. 1 (SECOND_CLOCK): SSP controller captures serial data on the second clock transition of the frame, that is, the transition back to the inter-frame state of the clock line. |
| SCR | Serial Clock Rate. The number of prescaler-output clocks per bit on the bus, minus one. Given that CPSDVSR is the prescale divider, and the APB clock PCLK clocks the prescaler, the bit frequency is PCLK / (CPSDVSR X [SCR+1]). |
| RESERVED | Reserved, user software should not write ones to reserved bits. The value read from a reserved bit is not defined. |