In this mode, it is possible to clear only the CH(n+1)F bit. Therefore, when the CH(n+1)F
bit is set again, the latest captured values are available in C(n)V and C(n+1)V registers.
For a new sequence of the measurements in the Dual Edge Capture – Continuous mode,
clear the CH(n)F and CH(n+1)F bits to start new measurements.
39.4.24.3 Pulse width measurement
If the channel (n) is configured to capture rising edges (ELS(n)B:ELS(n)A = 0:1) and the
channel (n+1) to capture falling edges (ELS(n+1)B:ELS(n+1)A = 1:0), then the positive
polarity pulse width is measured. If the channel (n) is configured to capture falling edges
(ELS(n)B:ELS(n)A = 1:0) and the channel (n+1) to capture rising edges (ELS(n
+1)B:ELS(n+1)A = 0:1), then the negative polarity pulse width is measured.
The pulse width measurement can be made in One-Shot Capture mode or Continuous
Capture mode.
The following figure shows an example of the Dual Edge Capture – One-Shot mode used
to measure the positive polarity pulse width. The DECAPEN bit selects the Dual Edge
Capture mode, so it remains set. The DECAP bit is set to enable the measurement of next
positive polarity pulse width. The CH(n)F bit is set when the first edge of this pulse is
detected, that is, the edge selected by ELS(n)B:ELS(n)A bits. The CH(n+1)F bit is set
and DECAP bit is cleared when the second edge of this pulse is detected, that is, the edge
selected by ELS(n+1)B:ELS(n+1)A bits. Both DECAP and CH(n+1)F bits indicate when
two edges of the pulse were captured and the C(n)V and C(n+1)V registers are ready for
reading.
Chapter 39 FlexTimer Module (FTM)
K22F Sub-Family Reference Manual, Rev. 4, 08/2016
NXP Semiconductors 1009
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