SPI signals

The XBee/XBee-PRO S2C DigiMesh 2.4 supports SPI communications in slave mode. Slave mode receives the clock signal and data from the master and returns data to the master. The SPI port uses the following signals on the device:

Signal	SMT pin #	SMT applicable AT command	TH Pin #	TH applicable AT command
SPI_MOSI (Master out, Slave in)	16	P6	11	D4
SPI_MISO (Master in, Slave out)	17	P5	4	P2
SPI_SCLK (Serial clock)	14	P8	18	D2
SPI_SSEL (Slave select)	15	P7	17	D3
SPI_ATTN (Attention)	12	P9	19	D1

By default, the inputs have pull-up resistors enabled. When the SPI pins are not connected but the pins are configured for SPI operation, then the device requires the pull-ups for proper UART operation.

Signal description

SPI_MISO: When SPI_CLK is active, the device outputs the data on SPI_MISO at the SPI_CLK rate. If there are other SPI slave devices connected to the same SPI master, then the SPI_MISO output from XBee device must be externally tri-stated when SPI_SSEL is de-asserted to prevent multiple devices from driving SPI_MISO.

SPI_MOSI: The SPI master outputs data on this line at the SPI_CLK rate after it selects the desired slave. When you configure the device for SPI operations, this pin is an input.

SPI_SCLK: The SPI master outputs a clock on this pin, and the rate must not exceed the maximum allowed, 5 Mb/s. This signal clocks data transfers on MOSI and MISO.

SPI_SSEL: The SPI master outputs a low signal on this pin to select the device as an SPI slave. When you configure the device for SPI operations, this pin is an input. This signal enables serial communication with the slave.

SPI_ATTN: The device asserts this pin low when it has data to send to the SPI master. When you configure this pin for SPI operations, it is an output (not tri-stated). This signal alerts the master that the slave has data queued to send. The device asserts this pin as soon as data is available to send to the SPI master and it remains asserted until the SPI master has clocked out all available data.