Silicon Laboratories EZRADIOPRO Si4060, Programming Manual

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7.6. SPI Communication Capture Example
Figure 15 shows an actual SPI communication capture taken by a logic analyzer. The signals being monitored are
SDI, SDO, and NSEL between the radio IC and the host MCU. The first command being sent is FIFO_INFO
(command ID 0x15) with an input parameter of 0x01, which will reset the TX FIFO. Right after sending the
FIFO_INFO command, the CTS is being monitored (0x44). For the first attempt, it is still busy; the returned value is
NOT 0xFF, so NSEL goes back high. For the second attempt, the CTS value will be 0xFF, meaning that the radio
IC has processed the command (i.e. resetting the TX_FIFO), and it is ready to provide the response bytes of the
FIFO_INFO command. Therefore, NSEL stays low, and two dummy bytes are provided via SDI to read out the two
response bytes through SDO. The response bytes are RX FIFO count and TX FIFO count numbers for the
FIFO_INFO command. The next sequence is sending GET_STATUS command with three input bytes, all zeroes,
to clear all ITs, and then retrieving the response bytes of the command after checking CTS. Once the ITs are
cleared, six bytes are being written to the TX FIFO via WRITE_TX_FIFO command (0x66). Lastly, START_TX
command is being sent to initiate an actual transmission. For more details of the commands described here, please
see the html-based API documentation.
Figure 15. SPI Communications Example