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Chapter 36 Input Capture
7.Q&A
7.6 How do I measure the pulse width of the input signal?
• "H" Width measurement:
Specify both edges for edge detection.
First detect the rising edge, then detect the falling edge.
Pulse width = {value recorded during falling (input capture register value)
+ “10000h” x Overflow frequency
– value recorded during rising (input capture register value)}
x Count clock width of free-run timer
Example: value recorded during falling = 2320h, Value recorded during rising = A635h,
Overflow frequency = 1, count clock = 125ns
==> pulse width = (2320h+10000h-A635h) x 125ns = 3997.375us
• Cycle measurement:
Specify rising (or falling) for edge detection.
Detect edge 2 times.
Cycle = {Second recorded value (input capture register value)
+ “10000h” x Overflow frequency
– First recorded value (input capture register value)}
x Count clock width of free-run timer
