How many counters are available on the PCC-DAS16/16AO (PC-CARD-DAS16/16AO)?

Last Modified: 3rd Jan 2013
Category: Data Acquisition > Measurement Computing
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Article Ref.: 13D1A
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PCMCIA 13D1A The PC-CARD-DAS16/16AO has 3 counters. However, two of these are used to divide down the frequency to the A/D pacer from the onboard clock. Therefore, only one counter (Counter 0) is available to the user for other uses, for example as an event counter. To access this counter, the example 8254 VI supplied with the Universal Library for LabVIEW can be used. The default location for this VI is: C:\Program Files\National Instruments\LabVIEW xx\examples\Universal Library\XCTR8254.VI This counter has several different modes, which are listed below. The datasheet for the counter is attached, which gives detailed information about these modes. The functions of the pins GATE, CLK and OUT depend on the mode that is selected. However, to generalise: The CLK pin function is typically where you would connect your TTL pulse train if you are counting TTL pulses or edges. The GATE pin function is usually some kind of trigger or enable\disable function. The OUT pin function typically outputs a value which is determined by (but not in general the same as) the input to CLK. Which mode is required for the counter depends on the application. MODES OF THE 8254 COUNTER ------------------------- The following information is copied from the Universal Library Reference guide. HIGHONLASTCOUNT Output of counter (OUT N) transitions from low to high on terminal count and remains high until reset. See Mode 0 on 8254 data sheet ONESHOT Output of counter (OUT N) transitions from high to low on rising edge of GATE N, then back to high on terminal count. See mode 1 on 8254 data sheet RATEGENERATOR Output of counter (OUT N) pulses low for one clock cycle on terminal count, reloads counter and recycles. See mode 2 on 8254 data sheet SQUAREWAVE Output of counter (OUT N) is high for count

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