ST25R95 datasheet(6/61 Pages) STMICROELECTRONICS

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Power management and operating modes

3.1

Operating modes

The ST25R95 has two operating modes: Wait for event (WFE) and Active. In Active mode, the ST25R95

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 ST25R95 can switch from one mode to another.

Table 3. ST25R95 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 ST25R95 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 ST25R95 waits for a command (ProtocolSelect, ...) from

the external host via the selected serial interface (SPI).

Reader

The ST25R95 can communicate with a tag using the selected protocol or with an external

host using the SPI interface.

Card

emulation

The ST25R95 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 ST25R95 via the SPI interface.

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 ST25R95 can no longer communicate with the

external host. It can only be woken up.

The behaviour of the ST25R95 in 'Tag detector' state is defined by the Idle command.

ST25R95

Power management and operating modes

DS12807 - Rev 4

page 6/61

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