ST25R3910 datasheet(29/65 Pages) STMICROELECTRONICS

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ST25R3910

Functional overview

During reception situation is similar. In case the FIFO is loaded with more data than the

receive water level, an interrupt is sent and the microcontroller in turn reads the data from

the FIFO.

When reception is finished an interrupt is sent to the microcontroller (INTR due to end of

receive), additionally the FIFO Status Register displays the number of bytes in the FIFO that

are still to be read out.

1.2.13

NFCIP-1 operation

The ST25R3910 supports only NFCIP-1 106 kbit/s active mode.

For operation in this mode, the bit nfc has to be set in the ISO Mode Definition Register.

Next, the NFCIP Field Detection Threshold Register has to be written to define the

thresholds for Target activation and RF Collision avoidance (see Section 1.1.5: External

field detector on page 8).

Note:

In the NFC mode the transmitter enable bit (tx_en) is never set in the Operation Control

NFCIP target

The ST25R3910 enters in the Initial NFC Target mode by setting the nfc_t bit in the

Operation Control Register. In this low power mode only the Target Activation Detector is

running.

When presence of an external the RF field is detected an interrupt is sent (INTR due to NFC

event). The microcontroller can now activate the oscillator, regulators and receiver. As

explained in Target Activation Detector, the Target Activation Detector may also be used to

detect the moment when initiator turns off its RF field. If the delay time after which the

initiator turns off its field after sending its request is known, this feature is not needed and

the Target Activation Detector can be turned off by setting bit nfc_t low after presence of the

initiator field is detected.

At this point direct command Unmask Receive Data has to be sent to put the Receiver and

control logic in the receive mode. The ST25R3910 is now ready to receive request from the

initiator. Procedure during the reception is the same as in case of the ISO-14443 mode.

The target response is done in the same way as in case of the ISO-14443 transmission,

only that the command which actually starts the transmission is either NFC transmit with

Response RF Collision Avoidance or NFC transmit with Response RF Collision Avoidance

with n=0. These two commands perform the RF Collision avoidance procedure before

actually starting the transmission. In case an external RF field is detected during the RF

Collision avoidance procedure an interrupt is sent (INTR due to NFC event) and the

transmission is not performed.

At this point the ST25R3910 is waiting for a new request from the initiator.

In case the Target Activation Detector is still enabled an interrupt will be generated when the

initiator switch on its field. This is additional information for the external controller, but it is

not required by the receiver. The receiver is already running, reception will be done

automatically and an interrupt will be sent when reception will be completed (or when the

FIFO water level will be reached in case of a long request).

ST25R3910 Datasheet(PDF) 29 Page - STMicroelectronics

ST25R3910 Datasheet(HTML) 29 Page - STMicroelectronics

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