The period measurement can be made in
The following figure shows an example of the Dual Edge Capture – One-Shot mode used
to measure the period between two consecutive rising edges. The DECAPEN bit selects
the Dual Edge Capture mode, so it remains set. The DECAP bit is set to enable the
measurement of next period. The CH(n)F bit is set when the first rising edge 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 rising edge 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 selected
edges were captured and the C(n)V and C(n+1)V registers are ready for reading.
channel (n) input
(after the filter
DECAPEN bit
C(n+1)V
FTM counter
clear CH(n+1)F
problem 2
2
1
2
3
channel input)
DECAP bit
set DECAPEN
set DECAP
5
6
7
8
10
3
4
6
5
Note
- The commands set DECAPEN, set DECAP, clear CH(n)F, and clear CH(n+1)F are made by the user.
4
9
11
12
13
14
6
15
16
17
18
19
20
21
22
23
24
25
26
27
28
17
20
15
20
23
C(n)V
CH(n+1)F bit
CH(n)F bit
clear CH(n)F
1
- Problem 1: channel (n) input = 0, set DECAP, not clear CH(n)F, and not clear CH(n+1)F.
- Problem 2: channel (n) input = 1, set DECAP, not clear CH(n)F, and clear CH(n+1)F.
- Problem 3: channel (n) input = 1, set DECAP, not clear CH(n)F, and not clear CH(n+1)F.
problem 3
problem 1
7
9
18
26
18
14
27
7
Figure 38-249. Dual Edge Capture – One-Shot mode to measure of the period between
two consecutive rising edges
Chapter 38 FlexTimer Module (FTM)
K22F Sub-Family Reference Manual , Rev. 3, 7/2014
Freescale Semiconductor, Inc.
933
Содержание MK22FN256VDC12
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