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52
CountTransitions
Type
Function returning Long
Invocation
CountTransitions(pin, interval)
Parameter
Method
Type
Description
pin
ByVal
Byte
The pin on which logic transitions will be counted.
interval
ByVal
Single or
Long
respectively, during which transitions will be counted.  See the
discussion below for information on range and resolution.
Discussion
When called, this routine will begin counting logic transitions on the specified pin and will continue until
the specified interval has elapsed.  During the counting process processor interrupts are disabled.  This
strategy allows high precision in measuring the interval but has the drawback that other processes that
utilize interrupts will not function correctly.  Among such affected processes are all serial communication
and multi-tasking.  For this reason, the counting interval should be kept as short as possible.  RTC ticks
that occur during the counting process are accumulated and the RTC is updated when the counting is
finished.
The specified pin, which you must configure to be an input before calling, is sampled at a fixed rate of
approximately 500KHz.  The default resolution of the measurement interval is approximately 2.441µS with
a maximum interval length of 5.2 seconds.  If the interval parameter is specified using a Single value
the units are seconds, otherwise the units are I/O Timer ticks where each tick is approximately 2.441 µS
(1/409.6KHz).  You may modify the range and resolution of the measurement interval by modifying the
built-in variable Register.TimerSpeed1.  See the special section on Timers for more details.
Resource Usage
This function uses the I/O Timer and disables interrupts during the counting process.  However, RTC ticks
are accumulated during the process and the RTC is updated upon completion.
Compatibility
In BasicX missed RTC ticks are not accounted for.
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