ADLINK Technology NuDAQ ACL-8454, Руководство пользователя

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Applications
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Applications
4.1 Timer / Counter Connection
The ACL-8454 has four 8254 chips on board. It offers 8 independent
16-bit programmable down counters and two pairs of cascaded
counters. To implement your application, you can following the
procedure to design your application and connect the signals.
1.
Check if use a clock source with fixed frequency, if answer is
‘No’ then go to step 7.
2. Calculate the frequency of clock according to your application
and decide the clock source: internal, external, or cascaded.
Then decided which counter is used.
3. If internal clock source is used, configure the CK n jumpers
according the calculation in step 2.
4. If external clock source is used, to generate a clock source
outside the board and check the frequency.
5. If cascaded clock source is used, to configure and program the
cascaded timer to generate the desired clock source.
6. If frequency of the clock is not fixed, only external source can be
used and then connect the external jump wires according your
application.
7. Decide the gate control source: always enable, externally
control, or cascaded controlled.
8. To connect or configure the gate signal of counter/timers.
9. To program the counter/timers using desired mode.