ASM330LHH datasheet(33/84 Pages) STMICROELECTRONICS

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ASM330LHH

Functionality

6.5

FIFO

The presence of a FIFO allows consistent power saving for the system since the host

processor does not need continuously poll data from the sensor, but It can wake up only

when needed and burst the significant data out from the FIFO.

The ASM330LHH embeds 3 kbytes of data in FIFO to store the following data:



Gyroscope



Accelerometer



Timestamp



Temperature

Writing data in the FIFO is triggered by the accelerometer / gyroscope data-ready signal.

The applications have maximum flexibility in choosing the rate of batching for physical

sensors with FIFO-dedicated configurations: accelerometer, gyroscope and temperature

sensor batching rates can be selected by the user. It is possible to select decimation for

timestamp batching in FIFO with a factor of 1, 8, or 32.

The reconstruction of a FIFO stream is a simple task thanks to the FIFO_DATA_OUT_TAG

byte that allows recognizing the meaning of a word in FIFO.

FIFO allows correct reconstruction of the timestamp information for each sensor stored in

FIFO. If a change in the ODR or BDR (Batching Data Rate) configuration is performed, the

application can correctly reconstruct the timestamp and know exactly when the change was

applied without disabling FIFO batching. FIFO stores information of the new configuration

and timestamp in which the change was applied in the device.

The programmable FIFO watermark threshold can be set in FIFO_CTRL1 (07h) and

FIFO_CTRL2 (08h) using the WTM[8:0] bits. To monitor the FIFO status, dedicated

registers (FIFO_STATUS1 (3Ah), FIFO_STATUS2 (3Bh)) can be read to detect FIFO

overrun events, FIFO full status, FIFO empty status, FIFO watermark status and the number

of unread samples stored in the FIFO. To generate dedicated interrupts on the INT1 and

INT2 pins of these status events, the configuration can be set in INT1_CTRL (0Dh) and

INT2_CTRL (0Eh).

The FIFO buffer can be configured according to six different modes:



Bypass mode



FIFO mode



Continuous mode



Continuous-to-FIFO mode



Bypass-to-continuous mode



Bypass-to-FIFO mode

Each mode is selected by the FIFO_MODE_[2:0] bits in the FIFO_CTRL4 (0Ah) register.

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