ST25R200 datasheet(68/88 Pages) STMICROELECTRONICS

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5.15.8

Calibrate WU measurement

The command calibrates the WU measurement.

The command is triggered manually and may also be automatically executed during WU mode (depending on

skip_cal and skip_recal configuration bits).

When executed from PD mode it first triggers the transition to RD mode, waits for the oscillator to become stable,

enables the field, and then performs the measurement.

In RD mode, it enables the field and then performs the measurement itself.

Calibration result available in the I/Q channel WU display calibration registers.

5.15.9

Clear WU calibration

The command clears the WU calibration to its default value.

Calibration result is available in the I/Q channel WU display calibration registers.

5.15.10

I/Q measurement and sense RF

These commands allow the user to measure the I and Q components of the RFI signal, whether it is an external

or self-emitted field.

The measurements are similar to the WU measurement but they can only be triggered once in RD mode and the

state of the transmitter is kept. Depending on tx_en it measures its own field, or check for the presence of an

external one.

Before executing the measurement, a clear WU calibration command shall be executed.

The measurement result is available at:

•

I/Q measurement: i_adc<7:0> and q_adc<7:0>

•

Sense RF: rf_ind<6:0> as a combination of I and Q

Note:

Both measurements take into account the configured gain, and calibration configuration. In the absence of the

self

‑emitted field, the external signal is not synchronous and may lead to uneven results. It may be used to

check for the presence of an external field, but not to accurately assess its intensity.

5.15.11

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 the signal BSS is kept high, that is, the following SPI command sent from the host

is automatically stopped the transparent mode.

5.15.12

Start GPT

This command manually starts the general purpose timer.

5.15.13

Start WUT

This command manually starts the wake-up timer.

5.15.14

Start MRT

This command manually starts the mark receive timer. Along with MRT, Start MRT command starts the NRT in

case nrt<15:0> ≠ 0.

5.15.15

Start NRT

This command manually starts the no response timer.

5.15.16

Stop NRT

This command manually stops the no response timer.

ST25R200

Application information

DS13658 - Rev 2

page 68/88

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