ISM330BX datasheet(43/150 Pages) STMICROELECTRONICS

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6.8.2

FIFO mode

In FIFO mode (FIFO_CTRL4 (0Ah)(FIFO_MODE_[2:0] = 001) data from the output channels are stored in the

FIFO until it is full.

To reset FIFO content, bypass mode should be selected by writing FIFO_CTRL4 (0Ah)(FIFO_MODE_[2:0]) to

000. After this reset command, it is possible to restart FIFO mode by writing FIFO_CTRL4 (0Ah)

(FIFO_MODE_[2:0]) to 001.

The FIFO buffer memorizes up to 4.5 KB of data (with compression enabled) but the depth of the FIFO can be

resized by setting the WTM[7:0] bits in FIFO_CTRL1 (07h). If the STOP_ON_WTM bit in FIFO_CTRL2 (08h) is

set to 1, FIFO depth is limited up to the WTM[7:0] bits in the FIFO_CTRL1 (07h) register.

6.8.3

Continuous mode

Continuous mode (FIFO_CTRL4 (0Ah)(FIFO_MODE_[2:0] = 110) provides a continuous FIFO update: as new

data arrives, the older data is discarded.

A FIFO threshold flag FIFO_STATUS2 (1Ch)(FIFO_WTM_IA) is asserted when the number of unread samples in

FIFO is greater than or equal to FIFO_CTRL1 (07h) (WTM[7:0]).

It is possible to route the FIFO_WTM_IA flag to the INT1 pin by writing in register INT1_CTRL (0Dh)

(INT1_FIFO_TH) = 1 or to the INT2 pin by writing in register INT2_CTRL (0Eh)(INT2_FIFO_TH) = 1.

A full-flag interrupt can be enabled, INT1_CTRL (0Dh)(INT1_FIFO_FULL) = 1 or INT2_CTRL (0Eh)

(INT2_FIFO_FULL) = 1, in order to indicate FIFO saturation and eventually read its content all at once.

If an overrun occurs, at least one of the oldest samples in FIFO has been overwritten and the FIFO_OVR_IA flag

in FIFO_STATUS2 (1Ch) 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_STATUS1 (1Bh) and FIFO_STATUS2 (1Ch)(DIFF_FIFO_[8:0]).

6.8.4

Continuous-to-FIFO mode

In continuous-to-FIFO mode (FIFO_CTRL4 (0Ah)(FIFO_MODE_[2:0] = 011), FIFO behavior changes according to

the trigger event detected in one of the following interrupt events:

•

Single tap

•

Double tap

•

Wake-up

•

Free-fall

•

D6D

When the selected trigger bit is equal to 1, FIFO operates in FIFO mode.

When the selected trigger bit is equal to 0, FIFO operates in continuous mode.

6.8.5

ContinuousWTM-to-full mode

In continuousWTM-to-full mode (FIFO_CTRL4 (0Ah)(FIFO_MODE_[2:0] = 010), FIFO behavior changes

according to the trigger event detected in one of the following interrupt events:

•

Single tap

•

Double tap

•

Wake-up

•

Free-fall

•

D6D

When the selected trigger bit is equal to 0, FIFO operates in continuous mode with the FIFO size limited to the

FIFO watermark level (defined by the WTM[7:0] bits in the FIFO_CTRL1 (07h) register).

When the selected trigger bit is equal to 1, FIFO continues to store data until it is full.

ISM330BX

Functionality

DS14588 - Rev 2

page 43/150

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