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4.2.3. Getting a Command Response from Radio
Reading from the radio requires several steps to be followed. The host MCU should send a command with the
address it requests to read. The radio holds the CTS while it retrieves the requested information. Once the CTS is
set (0xFF), the host MCU can read the answer from the radio.
Figure 10. Read Procedure
If the CTS is polled on the GPIOs, or the radio is configured to provide interrupt if the answer is available, then the
response can be read out from the radio with the following SPI transaction:
Figure 11. Read the Response from Radio
If the CTS is polled over the SPI bus, first the host MCU should pull the NSEL pin low. This action should be
followed by sending out the 0x44 Read command ID and providing an additional eight clock pulses on the SCLK
pin. The radio will provide the CTS byte on its SDO pin during the additional clock pulses. If the CTS byte is 0x00,
then the response is not yet ready and the host MCU should pull up the NSEL pin and repeat the procedure from
the beginning as long as the CTS byte is not 0xFF. If CTS is 0xFF, then the host MCU should keep the NSEL pin
low and provide clock cycles on the SCLK pin, as many as the data to be read out requires. The radio will clock out
the requested data on its SDO pin during the additional clock pulses.
Summary of Contents for Si4455 Series
Page 8: ...AN692 8 Rev 0 4 Figure 6 Device Configuration Options ...
Page 22: ...AN692 22 Rev 0 4 Figure 21 Supply Current versus Time Diagram from Shutdown to RX State ...
Page 23: ...AN692 Rev 0 4 23 4 4 Radio Chip Waking Up Figure 22 Radio Wake Up Process ...
Page 35: ...AN692 Rev 0 4 35 Figure 32 Transmission Flowchart ...
Page 39: ...AN692 Rev 0 4 39 Figure 33 Reception Flowchart ...
Page 41: ...AN692 Rev 0 4 41 Figure 34 Bidirectional Variable Packet Example Project Flowchart ...
Page 47: ...AN692 Rev 0 4 47 Figure 41 Long Packet Transmission Flowchart ...
Page 48: ...AN692 48 Rev 0 4 Figure 42 Long Packet RX Flowchart ...
