ST25R3916 datasheet(65/157 Pages) STMICROELECTRONICS

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DS12484 Rev 4

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ST25R3916/7

Application information

156

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

Calibrate capacitive sensor

This command calibrates the capacitive sensor.

It is strongly recommended to use this command in power-down mode only to avoid

interference with the crystal oscillator or reader magnetic field. Interrupt I_dct is only

generated in Ready mode. The measurement status is indicated by status bits in the

Capacitive sensor display register.

Duration time: 3 ms max.

This command is executed only if the capacitive sensor automatic calibration mode is set

(all bits cs_mcal in the Capacitive sensor control register are set to 0).

4.4.15

Measure capacitance

This command performs the capacitance measurement.

It is strongly recommended to use this command in power-down mode only to avoid

interference with the crystal oscillator or reader magnetic field.

Duration time: 250 μs max.

4.4.16

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.

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