RX95HF Datasheet, PDF (11/44 Pages) STMicroelectronics – Near field communication transceiver for tag emulation

RX95HF
4
Communication protocols
Communication protocols
4.1
4.1.1
Serial peripheral interface (SPI)
Polling mode
In order to send commands and receive replies, the application software has to perform 3
steps.
1. Send the command to the RX95HF.
2. Poll the RX95HF until it is ready to transmit the response.
3. Read the response.
The application software should never read data from the RX95HF without being sure that
the RX95HF is ready to send the response.
The maximum allowed SPI communication speed is f_SCK.
A Control byte is used to specify a communication type and direction:
 0x00: Send command to the RX95HF
 0x03: Poll the RX95HF
 0x02: Read data from the RX95HF
 0x01: Reset the RX95HF
The SPI_SS line is used to select a device on the common SPI bus. The SPI_SS pin is
active low.
When the SPI_SS line is inactive, all data sent by the Master device is ignored and the
MISO line remains in High Impedance state.
MOSI
Figure 6. Sending command to RX95HF
00000000
CMD
LEN
DATA
DATA
MISO
Control Byte
Several data bytes
XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX
Figure 7. Polling the RX95HF until it is ready
MOSI _{0 0 0 0 0 0 1 1 X X X X X X 1 1}
XXXXXX11 XXXXXX11
MISO
Control Byte
XXXXXXXX 00000XXX
Flag
Flag
00000XXX 00001XXX
Flags are polled until data is ready (Bit 3 is set when data is ready)
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