ASM330LXH datasheet(21/56 Pages) STMICROELECTRONICS

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ASM330LXH

Digital main block

3.2.2

FIFO mode

In FIFO mode (FIFO_CTRL(FMODE2:0) = 001) data from the output channels are stored in

the FIFO until it is overwritten.

To reset FIFO content, Bypass mode must be written in FIFO_CTRL(FMODE2:0), setting

these bits to '000' value. After this reset command it is possible to restart FIFO mode by

writing the value '001' in FIFO_CTRL(FMODE2:0).

The FIFO buffer can memorize up to 32 levels of data but the depth of the FIFO can be

resized by setting the CTRL4_C(STOP_ON_FTH) bit. If the STOP_ON_FTH bit is set to '1',

FIFO depth is limited to FIFO_CTRL(FTH4:0) + 1 data.

A FIFO threshold interrupt can be enabled (INT_OVR bit in INT_CTRL (0Dh)) in order to be

raised when the FIFO is filled to the level specified by the FTH4:0 bits of FIFO_CTRL (1Ah).

When a FIFO threshold interrupt occurs, the first data has been overwritten and the FIFO

stops collecting data from the input channels.

Figure 9. FIFO mode

3.2.3

Stream mode

Stream mode (FIFO_CTRL(FMODE2:0) = 010) provides continuous FIFO update: as new

data arrives, the older is discarded.

Once the whole FIFO has been read, the last data read remains in the FIFO and hence

once a new sample is acquired, the FIFO_SRC(FSS5:0) value rises from 0 to 2.

An overrun interrupt can be enabled, INT_CTRL(INT1_OVR) = '1', in order to inform when

the FIFO is full and eventually read its content all at once. If an overrun occurs, the oldest

sample in FIFO is overwritten, so if the FIFO was empty, the lost sample has already been

read.

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