FTM counter
NUMTOF[4:0]
TOF counter
set TOF bit
0x00
0x00
Figure 38-174. Periodic TOF when NUMTOF = 0x00
38.4.4 Input Capture mode
The Input Capture mode is selected when:
• DECAPEN = 0
• COMBINE = 0
• CPWMS = 0
• MSnB:MSnA = 0:0, and
• ELSnB:ELSnA ≠ 0:0
When a selected edge occurs on the channel input, the current value of the FTM counter
is captured into the CnV register, at the same time the CHnF bit is set and the channel
interrupt is generated if enabled by CHnIE = 1. See the following figure.
When a channel is configured for input capture, the FTMxCHn pin is an edge-sensitive
input. ELSnB:ELSnA control bits determine which edge, falling or rising, triggers input-
capture event. Note that the maximum frequency for the channel input signal to be
detected correctly is system clock divided by 4, which is required to meet Nyquist criteria
for signal sampling.
Writes to the CnV register is ignored in Input Capture mode.
While in BDM, the input capture function works as configured. When a selected edge
event occurs, the FTM counter value, which is frozen because of BDM, is captured into
the CnV register and the CHnF bit is set.
Chapter 38 FlexTimer Module (FTM)
K22F Sub-Family Reference Manual , Rev. 3, 7/2014
Freescale Semiconductor, Inc.
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