ADLINK cPCI-8554/R - Manual (Page 41)

Signal Connection and Applications • 31
4.3 Timer/Counter Connection
The cPCI/PCI-8554/R has four 8254 chips on board. It can offer 10
independent 16-bit programmable down counters with the option of
cascading the counters. To implement your application, the following
procedures should be followed.
1. Does the application require a fixed frequency, if answer is ‘No’,
an external clock source must be used. Go to step 3.
2. Calculate the frequency of the clock according to your
application requirements, then decide which clock source to use
(internal, external, or cascaded), and then decide which
counters to use.
3. If an external clock source is chosen, generate a clock signal
external to the cPCI/PCI-8554/R card and measure its frequency.
Determine whether the debounce function should be enabled or
disabled, and then set JP1 ~ JP10. If reserved counters 11 and
12 are required, set JP12 and JP13 to pin 2-3.
4. Decide the gate control source: always enable or external
controls, if gate control is necessary, connect the gate signal.
Note: Gate control of counter 11 and 12 are always enabled (tied to
logic high) and there are no gate control pins for counters 11
and 12 on CN1.
5. Program the counter/timer using the desired mode.