Hardware Reference
In-Depth Information
Pulse width
Rising edge
Falling edge
Figure 8.10 Pulse-width measurement using input-capture
Interrupt generation . All input-capture pins can serve as edge-sensitive interrupt
sources. Once enabled, interrupts will be generated on the selected edge(s).
Event counting . An event can be represented by a signal edge. An input-capture
channel can be used in conjunction with an output-compare function to count the
number of events that occur during an interval. An event counter can be set up
and incremented by the input-capture interrupt service routine. This application is
illustrated in Figure 8.11.
e 3
e 1
e 2
e 4
e i
e j
...
...
Start of
interval
End of
interval
Figure 8.11 Using an input-capture function for event counting
Time reference . In this application, an input-capture function is used in conjun-
ction with an output-compare function. For example, if the designer wants to
activate an output signal a certain number of clock cycles after detecting an input
event, the input-capture function would be used to record the time at which the
edge is detected. A number corresponding to the desired delay would be added to
this captured value and stored to an output-compare register. This application is
illustrated in Figure 8.12.
Time t 0
Time t 0 + delay
Time of reference
(set up by signal edge)
Time to activate
output signal
(set up by output-compare)
Figure 8.12 A time-reference application
Duty cycle measurement . The duty cycle is the percent of time that the signal is
high within a period in a periodic digital signal. The measurement of the duty cycle
is illustrated in Figure 8.13.
 
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