ST95HF Datasheet, PDF (64/93 Pages) STMicroelectronics – Dedicated internal frame controller

Additional Idle command description
Appendix A Additional Idle command description
ST95HF
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 ST95HF when it exits WFE mode.
The contents of the Wake-up event register can be read using the Read Register command
or in the ST95HF reply to the Idle command.
Bits [7:6]
Bit 5
LFO frequency RFU⁽¹⁾
1. Must be set to ‘0’.
Table 56. Wake-up source register
Bit 4
Bit 3
Bit 2
Bit 1
IRQ on pin SPI_SS IRQ on pin IRQ_IN Field Detect Tag Detect
Bit 0
Timeout
Bits [7:6]
LFO frequency
Bit 5
RFU
Table 57. Wake-up event register
Bit 4
Bit 3
Bit 2
Bit 1
IRQ on pin SPI_SS IRQ on pin IRQ_IN Field Detect Tag Detect
Bit 0
Timeout
Note:
Bits [7:6] define the LFO frequency (f_LFO):
00: 32 kHz 01: 16 kHz
10: 8 kHz 11: 4 kHz
Bit 4: When set, the ST95HF will wake up when an external interrupt (low level on pin
SPI_SS) is detected.
Bit 3: When set, the ST95HF 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 ST95HF will wake up when an RF field is detected.
Bit 1: When set, the ST95HF 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 ST95HF 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)*t_REF
t_REF= 256*t_L = 8 ms (f_LFO = 32 kHz), mean power consumption in Sleep mode is 25 µA
t_REF= 256*t_L = 64 ms (f_LFO = 4 kHz), mean power consumption in Sleep mode is 20 µA
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.
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