Bosch Sensortec"| BST-BMP581-DS004-02 23 | 74
Modifications reserved | Data subject to change
without notice Document number: BST-BMP581-DS004-02
0b01: Only Temperature data is stored (T-mode)
0b10: Only Pressure data is stored (P-mode)
0b11: Pressure and temperature data is stored (PT-mode)
The operational mode can be controlled via the FIFO_CONFIG.cfg_fifo_mode register:
1’b0: streaming mode
1’b1: stop on full mode
The two modes differ in how the FIFO reacts to an overflow. A FIFO overflow occurs if the FIFO is full and a new
measurement data is ready to be written to the FIFO. In streaming mode, the FIFO will delete the oldest frame, and
write the new frame to the FIFO. As a result, the FIFO contains always the most recent frames.
2
In stop-on-full mode, frames once written to the FIFO will not be discarded. Instead, new frames will not be written to
the FIFO until there is space again.
The FIFO decimation factor (or downsampling) can be adjusted With FIFO_SEL.cfg_fifo_dec_sel. Only every n-th
sample will be written to the FIFO, where:
= 2
_.___
The FIFO threshold can be set by FIFO_CONFIG_fifo_threshold. If the fill level of the FIFO reaches the threshold,
the FIFO threshold interrupt may be triggered (see Chapter 3.7.2.1). The meaning of the register field is the following:
0x00: FIFO threshold disablef
0x01..0x1F (or 1..31 decimal): threshold level
0x0F: 15 frames. This is the maximum setting in PT-mode. The most significant bit is ignored.
0x1F: 31 frames. This is the maximum setting in P- or T-mode.
4.6.2 FIFO status
The fill level of the FIFO in number of frames can be obtained from FIFO_COUNT.fifo_count. FIFO watermark and
FIFO full information can be obtain from the interrupt functionality (see Chapter 3.7.2.1).
4.6.3 FIFO data readout
The FIFO can be read out by reading in a burst from register FIFO_DATA.
Reads should be performed in the granularity of the frame size (24 or 48 bit) according to the selected frame type.
Frames that have been read incompletely will stay in the FIFO memory and will be retransmitted on the next read. The
entire FIFO contents can be read in one single burst.
If the FIFO is empty, disabled or turns empty during a read, it will return the empty frame, which is 0x7f.
Table 10,
Table 11 and Table 13 show the frame formats for the three different frame kinds: PT, T and P. The empty frame is
shown in Table 13.
Table 11: FIFO pressure and temperature frame (PT-fram
2. In order to work properly, streaming mode requires that the clock frequency of host interface is 0.1MHz or above. Otherwise, the
FIFO readout bandwidth could be slower than the FIFO write bandwidth, which will cause data loss.
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