AIS2IH datasheet(23/63 Pages) STMICROELECTRONICS

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5.3.3

Continuous mode

Continuous mode (FIFO_CTRL (2Eh)(FMode[2:0] = 110) provides a continuous FIFO update: when 32 unread

samples are stored in memory, as new data arrives the oldest data is discarded and overwritten by the newer.

A FIFO threshold flag FIFO_SAMPLES (2Fh)(FIFO_FTH) is asserted when the number of unread samples in

FIFO is greater than or equal to (FIFO_CTRL (2Eh)FTH[4:0]).

It is possible to route FIFO_SAMPLES (2Fh)(FTH) to the INT1 pin by writing the INT1_FTH bit to '1' in

CTRL5_INT2_PAD_CTRL (24h).

If an overrun occurs, the oldest sample in FIFO is overwritten and the FIFO_OVR flag in FIFO_SAMPLES (2Fh) is

asserted.

In order to empty the FIFO before it is full, it is also possible to pull from FIFO the number of unread samples

available in FIFO_SAMPLES (2Fh)(Diff[5:0]).

5.3.4

Continuous-to-FIFO mode

In Continuous-to-FIFO mode FIFO_CTRL (2Eh)(FMode[2:0] = 011), FIFO operates in Continuous mode and FIFO

mode starts upon an internal trigger event. When the FIFO is full, data collecting is stopped. The trigger could be

a wake-up, free-fall, 6D interrupt event or any combination of these events, but every interrupt has to be routed on

the corresponding pad to be used as a trigger.

Figure 8. Continuous-to-FIFO mode

x31

y31

z31

xi,yi,zi

Continuous Mode

FIFO Mode

Trigger event

x31

y31

z31

xi,yi,zi

x30

y30

z30

Figure 9. Trigger event to FIFO for Continuous-to-FIFO mode

AIS2IH

FIFO

DS12421 - Rev 4

page 23/63

AIS2IH Datasheet(PDF) 23 Page - STMicroelectronics