Digital I/O

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PCI 6509 Read Input timing

I am reading some (7) digitial input lines from the 6509 using the DAQmx driver (7.4) command DAQmxReadDigitalLines().  What type of timing requirements do I need for this?  That is:
  •  the data setup time ( the time that the inputs must be stable to ensure a stable output),
  • and how long will the read take?
Thanks.... Gordon
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Hello Gordon,

The NI PCI-6509 is a completely software timed DIO card.  This means that the setup time and acquisition time for a digital input operation are dependant on how fast your computer can execute software commands.  There is no internal sample clock on these boards to be used to clock a digital input or output operation.  The time required to perform consecutive digital reads using the DAQmxReadDigitalLines() in a loop will depend on how fast your system can process and send commands to the NI PCI-6509.  For clocked digital input and output operations, you will need a High Speed Digital board (653x family) or M-series board.

For more information on the difference between software and hardware timing, check out the section in the NI-DAQmx Help about timing. (
NI-DAQmx Key Concepts >> Timing and Triggering >> Timing).

I hope this helps!

Travis G.

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