LSM303AH Datasheet, PDF (33/82 Pages) –

LSM303AH
Functionality
4.4.2
4.4.3
4.4.4
FIFO mode
In FIFO mode (FIFO_CTRL_A (25h) (FMODE [2:0])= 001) data from the X, Y and Z
channels are stored in the FIFO until it is full, when 256 unread samples are stored in
memory, data collecting is stopped.
To reset the FIFO content, Bypass mode should be written in the FIFO_CTRL_A (25h)
register, setting the FMODE [2:0] bits to '000'. After this reset command, it is possible to
restart FIFO mode, writing the value '001' in FIFO_CTRL_A (25h) (FMODE [2:0]).
The FIFO buffer can memorize 256 slots of X, Y and Z data.
Continuous mode
Continuous mode (FIFO_CTRL_A (25h) (FMODE[2:0] = 110) provides a continuous FIFO
update: when 256 unread samples are stored in memory, as new data arrives the oldest
data is discarded and overwritten by the newer.
A FIFO threshold flag FIFO_CTRL_A (25h) (FIFO_FTH) is asserted when the number of
unread samples in FIFO is greater than or equal to FIFO_THS_A (2Eh) (FTH[7:0]).
It is possible to route FIFO_CTRL_A (25h)(FTH) to the INT1 pin by writing the INT1_FTH bit
to '1' in register CTRL4_A (23h) or to the INT2 pin by writing the INT2_FTH bit to '1' in
register CTRL5_A (24h).
If an overrun occurs, the oldest sample in FIFO is overwritten and the FIFO_OVR flag in
FIFO_SRC_A (2Fh) 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 in FIFO_SRC_A (2Fh) and FIFO_SAMPLES_A (30h) (Diff[8:0]).
Continuous-to-FIFO mode
In Continuous-to-FIFO mode FIFO_CTRL_A (25h) (FMODE [2:0] = 011), FIFO operates in
Continuous mode and FIFO mode starts upon an internal trigger event. When the FIFO is
full, data collecting is stopped.
Figure 8. Continuous-to-FIFO mode
x_i,y_i,z_i
x₀
y₀
z₀
x₁
y₁
z₁
x₂
y₂
z₂
x₃₀
y₃₀
z₃₀
x₃₁
y₃₁
z₃₁
x_i,y_i,z_i
x₀
y₀
z₀
x₁
y₁
z₁
x₂
y₂
z₂
x₃₁
y₃₁
z₃₁
Continuous Mode
Trigger event
FIFO Mode
DocID027766 Rev 6
33/82
82