PC104-PLUS1500
Functions of the board
37
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Clock: The counter counts at positive or negative edge or with each edge
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Trigger function: Sets the counter on its start value 0 in the
upwards mode = clear function
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Clear function: The counter status is deleted. (counting value set on 0)
a) Upwards counter
Function upwards counter:
The counter starts with counter value 0 and increments with each valid edge. At
the result of count reload value -1, with the following valid edge the counter is set
on 0. An interrupt can be generated with the overflow.
Software clear:
Deletes counter (= 0)
Software trigger:
Sets counter (= 0)
Example upwards counter
Reload value = 9
Initialisation on rising edge
Interrupt is released
At the current result of count = 8 (reload value -1) with the following valid edge
the counter is deleted and the interrupt enabled, i.e. after reaching the reload value
the counting value is set on 0 and the counting will be continued.
Fig.8-5: Upwards counter