ASM330LHH datasheet(34/84 Pages) STMICROELECTRONICS

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Functionality

ASM330LHH

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DocID031239 Rev 4

6.5.1

Bypass mode

In Bypass mode (FIFO_CTRL4 (0Ah)(FIFO_MODE_[2:0] = 000), the FIFO is not operational

and it remains empty. Bypass mode is also used to reset the FIFO when in FIFO mode.

6.5.2

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 3 kbytes of data but the depth of the FIFO can be resized

by setting the WTM [8:0] bits in FIFO_CTRL1 (07h) and FIFO_CTRL2 (08h). If the

STOP_ON_WTM bit in FIFO_CTRL2 (08h) is set to '1', FIFO depth is limited up to the WTM

[8:0] bits in FIFO_CTRL1 (07h) and FIFO_CTRL2 (08h).

6.5.3

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 (3Bh)(FIFO_WTM_IA) is asserted when the number

of unread samples in FIFO is greater than or equal to FIFO_CTRL1 (07h) and FIFO_CTRL2

(08h)(WTM [8:0]).

It is possible to route the FIFO_WTM_IA flag to FIFO_CTRL2 (08h) to the INT1 pin by

writing in register INT1_CTRL (0Dh)(INT1_FIFO_TH) = '1' or to the INT2 pin by writing in

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 (3Bh) 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 inFIFO_STATUS1 (3Ah) and FIFO_STATUS2

(3Bh)(DIFF_FIFO_[9:0]).

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