ST25R95 datasheet(54/61 Pages) STMICROELECTRONICS

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Additional Idle command description

This section provides examples of use for the Idle command.

The wake-up source is the third of the 16 bytes in the Idle command. This byte specifies authorized Wake-up

events. This revision now also provides the capability to set the LFO frequency in WFE mode.

The LFO frequency and the authorized wake-up source settings are stored in the Wake-up source register as the

parameters of the Idle command.

The Wake-up event is updated by the ST25R95 when it exits WFE mode.

The contents of the Wake-up event register can be read using the Read Register command or in the ST25R95

reply to the Idle command.

Table 56. Wake-up source register

Bits [7:6]

Bit 5

Bit 4

Bit 3

Bit 2

Bit 1

Bit 0

LFO frequency

RFU (1)

IRQ on pin SPI_SS

IRQ on pin IRQ_IN

Field Detect

Tag Detect

Timeout

1. Must be set to ‘0’.

Table 57. Wake-up event register

Bits [7:6]

Bit 5

Bit 4

Bit 3

Bit 2

Bit 1

Bit 0

LFO frequency

RFU

IRQ on pin SPI_SS

IRQ on pin IRQ_IN

Field Detect

Tag Detect

Timeout

Bits [7:6] define the LFO frequency (fLFO):

00: 32 kHz

01: 16 kHz

10: 8 kHz

11: 4 kHz

Bit 4: When set, the ST25R95 will wake up when an external interrupt (low level on pin SPI_SS) is detected.

Bit 3: When set, the ST25R95 will wake up when an external interrupt (low level on pin IRQ_IN) is detected. This

is useful for SPI communication. It is recommended to set this bit to ‘1’ in order to recover in the event of a system

crash.

Bit 2: When set, the ST25R95 will wake up when an RF field is detected.

Bit 1: When set, the ST25R95 will wake up when a tag is detected in the RF field. This bit must also be set during

Tag detection calibration or during a Tag detection sequence.

Bit 0: When set, the ST25R95 will wake up and return to Ready state at the end of a predefined cycle. The

Timeout (TO) value is defined by the MaxSleep and Wake-up period:

TO = (MaxSleep+1)*(WuPeriod+2)*tREF

tREF= 256*tL = 8 ms (fLFO = 32 kHz), mean power consumption in sleep mode is 25 µA

tREF= 256*tL = 64 ms (fLFO = 4 kHz), mean power consumption in sleep mode is 20 µA

Note:

0x00 < MaxSleep < 0x1F.

This bit must be set when using the timer as a possible wake-up source. It must be set during Tag detection

calibration to force a wake-up after the first Tag detection trial.

ST25R95

Additional Idle command description

DS12807 - Rev 4

page 54/61

ST25R95 Datasheet(PDF) 54 Page - STMicroelectronics

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