STRFNFCA datasheet(57/74 Pages) STMICROELECTRONICS

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STRFNFCA

Additional Idle command description

Doc ID 023077 Rev 10

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Appendix A

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 STRFNFCA when it exits WFE mode.

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

or in the STRFNFCA reply to the Idle command.

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 STRFNFCA will wake up when an external interrupt (low level on pin

SPI_SS) is detected. This is useful for UART communication.

Bit 3: When set, the STRFNFCA 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 STRFNFCA will wake up when an RF field is detected.

Bit 1: When set, the STRFNFCA 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 STRFNFCA 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 *(WuPeriod+1)*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:

Note that: 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.

Table 48.

Wake-up source register

Bits [7:6]

Bit 5

Bit 4

Bit 3

Bit 2

Bit 1

Bit 0

LFO frequency

RFU(1)

Must be set to ‘0’.

IRQ on pin

SPI_SS

IRQ on pin

IRQ_IN

Field Detect

Tag Detect

Timeout

Table 49.

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

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