ST25R3916 datasheet(36/157 Pages) STMICROELECTRONICS

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Application information

ST25R3916/7

36/157

DS12484 Rev 4

In the opposite case, when no tag response is being processed, the receiver is

disabled.

The NRT can also be started using direct command Start No-response timer. The intention

of this command is to extend the No-response timer timeout beyond the range defined in the

No-response timer control registers. If this command is sent while the timer is running, it is

reset and restarted.

The NRT can be terminated using direct command Stop No-response Timer or Stop all

activities. The timer is terminated and no IRQ is sent. It is expected to be used in the

nrt_emv mode, when the incoming reception does not stop the No-response timer.

In the NFCIP-1 active communication mode the NRT role is similar to operation in the

normal Reader mode. If the NRT expires before the start of a response is detected an IRQ is

produced and the receiver is disabled. There are two modes available:



nrt_nfc = 0

–

The timer is started when the device TX field is switched off, using a general

purpose timer.

–

The operation is valid for active initiator and target modes as well as for bit rate

detection mode.



nrt_nfc = 1

–

The timer is started when the peer field is turned on.

–

Operation is valid for Active initiator and Active target modes.

For Bit rate detection mode the timer is not started at peer field on as, in case of migration

from Bit rate detection mode to Active target mode, the MCU has to reconfigure the device

to Active target mode prior field on.

In the NFCIP-1 Passive target the No-response timer has no task and is not automatically

started.

PPON2 timer

This timer is not used in Reader mode.

In NFCIP-1 mode this timer is automatically started when the transmitter is turned off after

the message has been sent. If this timer expires before the peer NFC device

(TFADT +n*TRFW) field-on is detected, an I_ppon2 IRQ is sent.

If the external RF field is detected on time, the timer is stopped and no IRQ is sent.

Time is defined in the PPON2 field waiting register.

General purpose (GP) timer

The triggering of the this timer is configured by setting the Timer and EMV control register. It

can be used to survey the duration of reception process (triggering by start of reception,

after SOF) or to time out the PCD to PICC response time (triggered by end of reception,

after EOF).

In the NFCIP-1 active communication mode it is used to timeout the field switching off. In all

cases an IRQ is sent when it expires.

The GP timer can also be started by sending the direct command Start General purpose

timer. If this command is sent while the timer is running, it is reset and restarted.

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