LSM303AGR datasheet(31/68 Pages) STMICROELECTRONICS

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LSM303AGR

Functionality

An overrun interrupt can be enabled, I1_OVERRUN = '1' in the CTRL_REG3_A (22h)

interrupt occurs, the first data has been overwritten and the FIFO stops collecting data from

the input channels.

After the last read it is necessary to exit Bypass mode in order to reset the FIFO content.

After this reset command, it is possible to restart FIFO mode just by selecting the FIFO

mode configuration (FM[1:0] bits) in register FIFO_CTRL_REG_A (2Eh).

4.4.3

Stream mode

In Stream mode the FIFO continues filling data from the X, Y, and Z accelerometer channels

until the buffer is full (a set of 32 samples stored) at which point the FIFO buffer index

restarts from the beginning and older data is replaced by the current data. The oldest values

continue to be overwritten until a read operation frees the FIFO slots.

An overrun interrupt can be enabled, I_XL_OVERRUN = '1' in the CTRL_REG3_A (22h)

mandatory not to lose data and it is not possible to read at least one sample for each axis

within one ODR period, a watermark interrupt can be enabled in order to read partially the

FIFO and leave memory slots free for incoming data.

Setting the FTH [4:0] bit in the FIFO_CTRL_REG_A (2Eh) register to an N value, the

number of X, Y and Z data samples that should be read at the rise of the watermark interrupt

is up to (N+1).

Figure 8. Stream mode

4.4.4

Stream-to-FIFO mode

In Stream-to-FIFO mode, data from the X, Y and Z accelerometer channels are collected in

a combination of Stream mode and FIFO mode. The FIFO buffer starts operating in Stream

mode and switches to FIFO mode when the selected interrupt occurs.

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