lis3dsh STMicroelectronics, lis3dsh Datasheet - Page 21

• Manufacturer Part Number: lis3dsh
• Description: Mems Digital Output Motion Sensor Ultra Low-power High Performance Three-axis “nano” Accelerometer
• Manufacturer: STMicroelectronics

LIS3DSH
5.2
5.2.1
5.2.2
5.2.3
5.2.4
5.2.5
FIFO
LIS3DSH embeds an acceleration data FIFO for each of the three output channels, X, Y,
and Z. This allows a consistent power saving for the system, since the host processor does
not need to continuously poll data from the sensor, but it can wake up only when needed
and burst the significant data out from the FIFO. This buffer can work according to four
different modes: Bypass mode, FIFO mode, Stream mode and Stream-to-FIFO mode. Each
mode is selected by the FIFO_MODE bits. Programmable Watermark level, FIFO_empty or
FIFO_Full events can be enabled to generate dedicated interrupts on the INT1/2 pin.
Bypass mode
In Bypass mode, the FIFO is not operational and for this reason it remains empty. For each
channel only the first address is used. The remaining FIFO slots are empty.
FIFO mode
In FIFO mode, data from X, Y, and Z channels are stored in the FIFO. A Watermark interrupt
can be enabled in order to be raised when the FIFO is filled to the level specified by the
internal register. The FIFO continues filling until it is full. When full, the FIFO stops collecting
data from the input channels.
Stream mode
In Stream mode, data from the X, Y, and Z measurement are stored in the FIFO. A
Watermark interrupt can be enabled and set as in the FIFO mode. The FIFO continues filling
until it’s full. When full, the FIFO discards the older data as the new arrive.
Stream-to-FIFO mode
In Stream-to_FIFO mode, data from the X, Y, and Z measurement are stored in the FIFO. A
Watermark interrupt can be enabled in order to be raised when the FIFO is filled to the level
specified by the internal register. The FIFO continues filling until it’s full. When full, the FIFO
discards the older data as the new arrive. Once trigger event occurs, the FIFO starts
operating in FIFO mode.
Retrieve data from FIFO
FIFO data is read through the OUT_X, OUT_Y and OUT_Z registers. When the FIFO is in
Stream, Trigger or FIFO mode, a read operation to the OUT_X, OUT_Y or OUT_Z registers
provides the data stored in the FIFO. Each time data is read from the FIFO, the oldest X, Y,
and Z data are placed in the OUT_X, OUT_Y and OUT_Z registers and both single read and
read_burst operations can be used.
Doc ID 022405 Rev 1
Digital main blocks
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