STRFNFCA datasheet(8/74 Pages) STMICROELECTRONICS

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Power management and operating modes

STRFNFCA

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Doc ID 023077 Rev 10

Power management and operating modes

3.1

Operating modes

The STRFNFCA has 2 operating modes: Wait for Event (WFE) and Active. In Active mode,

the STRFNFCA communicates actively with a tag or an external host (an MCU, for

example). WFE mode includes four low consumption states: Power-up, Hibernate,

Sleep/Field Detector and Tag Detector.

The STRFNFCA can switch from one mode to another.

Hibernate, Tag Detector, and Sleep/Field Detector states can only be activated by a

command from the external host. As soon as any of these three states are activated, the

STRFNFCA can no longer communicate with the external host. It can only be woken up.

The behavior of the STRFNFCA in 'Tag Detector' state is defined by the Idle command.

Table 3.

STRFNFCA operating modes and states

Mode

State

Description

Wait For

Event

(WFE)

Power-up

This mode is accessible directly after POR.

Low level on IRQ_IN pin (longer than 10 µs) is the only wakeup

source. LFO (low-frequency oscillator) is running in this state.

Hibernate

Lowest power consumption state. The STRFNFCA has to be woken-

up in order to communicate. Low level on IRQ_IN pin (longer than 10

µs) is the only wakeup source.

Sleep/Field

Detector

Low power consumption state. Wakeup source is configurable:

–Timer

–IRQ_IN pin

– SPI_SS pin

– Field Detector

LFO (low-frequency oscillator) is running in this state.

Tag Detector

Low power consumption state with tag detection. Wakeup source is

configurable:

–Timer

–IRQ_IN pin

– SPI_SS pin

– Tag detector

LFO (low-frequency oscillator) is running in this state.

Active

Ready

In this mode, the RF is OFF and the STRFNFCA waits for a

command (PROTOCOLSELECT, ...) from the external host via the

selected serial interface (UART or SPI).

Reader

The STRFNFCA can communicate with a tag using the selected

protocol or with an external host using the selected serial interface

(UART or SPI).

Card Emulation

The STRFNFCA can communicate as a Card or Tag with an external

reader. The Card or Tag application is located in the Host and

communicates with the STRFNFCA via the serial interface (SPI).

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