ST95HF datasheet(12/93 Pages) STMICROELECTRONICS

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Power management and operating modes

ST95HF

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Power management and operating modes

3.1

Operating modes

The ST95HF has 2 operating modes: Wait for Event (WFE) and Active. In Active mode, the

ST95HF 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 ST95HF 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

ST95HF can no longer communicate with the external host. It can only be woken up.

The behavior of the ST95HF in 'Tag Detector' state is defined by the Idle command.

Table 3. ST95HF 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 ST95HF 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 ST95HF waits for a command

(PROTOCOLSELECT, ...) from the external host via the selected serial

interface (SPI).

Reader

The ST95HF can communicate with a tag using the selected protocol

or with an external host using the SPI interface.

Card Emulation

The ST95HF 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 ST95HF via the SPI interface.

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