Control B

0x01 [ID-000004d0]

Bit 7 – BUFEN: Buffer Mode Enable

Buffer Mode Enable

Writing this bit to '1' enables Buffer Mode, meaning two buffers in receive direction, one buffer in transmit direction, and separate interrupt flags for both transmit complete and receive complete.

Bit 6 – BUFWR: Buffer Mode Wait for Receive

Buffer Mode Wait for Receive

When writing this bit to '0' the first data transferred will be a dummy sample.

0 One SPI transfer must be completed before the data is copied into the shift register.
1 When writing to the data register when the SPI is enabled and SS is high, the first write will go directly to the shift register.

Bit 2 – SSD: Slave Select Disable

Slave Select Disable

When this bit is set and when operating as SPI Master (MASTER=1 in SPI.CTRLA), SS does not disable Master Mode.

0 Enable the Slave Select line when operating as SPI Master.
1 Disable the Slave Select line when operating as SPI Master.

Bits 1:0 – MODE[1:0]: Mode


These bits select the transfer mode. The four combinations of SCK phase and polarity with respect to the serial data are shown in the table below. These bits decide whether the first edge of a clock cycle (leading edge) is rising or falling, and whether data setup and sample occur on the leading or trailing edge. When the leading edge is rising, the SCK signal is low when idle, and when the leading edge is falling, the SCK signal is high when idle.

0x0 0

Leading edge: Rising, sample
Trailing edge: Falling, setup

0x1 1

Leading edge: Rising, setup
Trailing edge: Falling, sample

0x2 2

Leading edge: Falling, sample
Trailing edge: Rising, setup

0x3 3

Leading edge: Falling, setup
Trailing edge: Rising, sample