ST25R3920B datasheet(64/158 Pages) STMICROELECTRONICS

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Application information

ST25R3920B

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DS13890 Rev 4

Duration time: 5 ms max.

This command is not accepted if external definition of the regulated voltage is selected in

the Regulator voltage control register (bit reg_s is set to 1).

4.4.11

Measure phase

This command measures the phase difference between the signals on the RFO outputs and

the signals on the RFI inputs and stores the result in the A/D converter output register.

This command enables the transmitter and phase detector, and performs an A/D conversion

of the output of the phase detector with the A/D converter in relative mode. The phase

measurement results can be calculated using the following formulas:

•

0 ≤ Φ ≤ 17º: result = 255

•

17 < Φ < 163º: angle [º] = 17 + (1 -result / 255) * 146

•

163 ≥ Φ ≥ 180º: result = 0

Duration time: 25 μs max.

4.4.12

Clear RSSI

The receiver automatically clears the RSSI bits in the RSSI display register and starts a new

measurement of the RSSI when a new reception is started (e.g. after a Transmit direct

command). Since the RSSI bits store the peak value (peak-hold type) eventual variation of

the receiver input signal will not be followed (this may happen in case of a long message or

test procedure).

The direct command Clear RSSI clears the RSSI bits in the RSSI display register, and

restarts the RSSI measurement. This allows to obtain multiple RSSI measurements during a

single reception.

4.4.13

Transparent mode

This command sets the receiver and transmitter into the transparent mode. The device

enters the transparent mode on the rising edge of the BSS signal of the SPI frame used to

send the direct command. The transparent mode is maintained as long as signal BSS is

kept high, that is, the following SPI command sent from the microcontroller will automatically

stop the transparent mode.

4.4.14

Measure power supply

This command measures the power supply. The bits mpsv<2:0> in the Regulator voltage

control register select which signal is measured. The result of the measurement is stored in

the A/D converter output register.

For power supply measurements the selected supply input voltage is divided by three and

measured with the A/D converter in absolute mode. This leads to a resolution of 23.4 mV

per LSB for all power supply measurements.

Duration time: 25 μs max.

4.4.15

Trigger RC calibration

The command triggers the RC calibration cycle for the active waveshaping filter constant.

The result can be read in AWS time 6 register and IRQ I_dct signals end of calibration.

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