Information

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 keeps set in all operation mode. 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
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Note
- The commands set DECAPEN, set DECAP, clear CH(n)F, and clear CH(n+1)F are made by the user.
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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
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18 26
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7
Figure 37-247. Dual Edge Capture – One-Shot Mode to Measure of the Period Between
Two Consecutive Rising Edges
The following figure shows an example of the dual edge capture – continuous mode used
to measure the period between two consecutive rising edges. The DECAPEN bit selects
the dual edge capture mode, so it keeps set in all operation mode. While the DECAP bit
is set the configured measurements are made. The CH(n)F bit is set when the first rising
Chapter 37 FlexTimer (FTM)
K10 Sub-Family Reference Manual, Rev. 6, Nov 2011
Freescale Semiconductor, Inc. 997