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APCI-1032, APCI-1564 and APCI-2032
8.4
Timer
The 12-bit timer is a downward counter which generates an interrupt after the reload
value has run down (timeout). Through timer, a time base can be defined independently
from the PC clock and synchronise operations for example.
The status of the counter value, the reload value and of the interrupt register can be read
back through software.
8.5
Counter (APCI-1564)
3 x 32-bit counter inputs are available on the board APCI-1564. They have the same
functions as a 82C54 counter component. Each counter can be programmed through
software.
The counter inputs are connected through the channels 0 to 2. When the counter
function is not used, the inputs are connected as regular digital inputs.
A counter has the following technical features:
2 counter modes: the counter can be programmed as an up or down counter.
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After reaching the reload value or when the counter has run down, an interrupt can
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be generated.
Reload value, 32-bit
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Clock: the counter counts at rising or falling edge or with each input pulse.
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Trigger function: sets the counter back to its start value
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0: start value by up counting = clear function
Reload value: start value by down counting
Clear function: the counter status is cleared (reload value and counter value set to 0)
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The 3 counters can be simultaneously initialised, started or stopped by synchronous
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control.
The status of the input 0 to 2 can be read back through external clock.
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Up counter
After reaching the reload value, the counter value is set to 0 and counts on.
An interrupt can be generated by overflow.
52
Fig. 8-10: Function of the up counter
Functions of the board
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