AN4506 查看數據表（PDF） - STMicroelectronics
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AN4506 Datasheet PDF : 47 Pages
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First-in first-out (FIFO) buffer
AN4506
As described for FIFO mode, data can be retrieved when OVRN is set to “1” performing a 32
sample set reading from the output registers; data can be retrieved also on the FTH flag if
the application requires a lower number of samples (see Section 6.3.4).
Figure 20. Stream mode fast reading behavior
F0 F1 F2 F3 F4 F5 … … F31 F0 F1 … F31F0 F1 …
…
0 1 2 3 4 5 … … 31 3233 … 63 6465 …
…
FIFO Reading
OVRN
Stream
enable
Start FIFO
Reading
Start FIFO
Reading
t
AM08474v1
In Stream mode, the FIFO buffer is continuously filling (from F0 to F31) at the selected
output data rate. When the buffer is full, the OVRN flag goes high and the recommended
solution is to read all FIFO samples (192 bytes) faster than 1*ODR, in order to free FIFO
slots available for the new angular rate samples. This allows avoiding loss of data and
limiting intervention from the host processor which increases system efficiency. If the read is
not fast enough, three different cases can be observed:
1. FIFO sample set (6 bytes) is read faster than 1*ODR: data are correctly retrieved
because a free slot is made available before new data is generated.
2. FIFO sample set (6 bytes) is read synchronous to 1*ODR: data are correctly retrieved
because a free slot is made available before new data is generated but FIFO benefits
are not exploited. This case is equivalent to reading data on data-ready interrupt and
does not reduce intervention from the host processor compared to the standard
gyroscope reading.
3. FIFO sample set (6 bytes) is read slower than 1*ODR; in this case some data are lost
because data recovery is not fast enough to free slots for new angular rate data (refer
to Figure 21). The number of correctly recovered samples is related to the difference
between the current ODR and the FIFO sample set reading rate.
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