Digital I/O

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6533 to 6356/7/8 Cable Adapter - PFI lines and digital input sample clock

I am updating some old code that was written for the NI PCI-6533 32-HS digital I/O card and think I now understand what is going on but was hoping someone could confirm I'm on the right track.


The old code sets the sample clock to external using the traditional NI-DAQ DIG_BLOCK_PG_CONFIG method and passing 1 as the reqSource parameter. The documentation I have says this uses the REQ pin on the I/O connector. In the 6536/7/8 cable adapter user guide, there is a diagram showing an example configuration of PFI line mapping that takes PFI2 from the 6533 side and jumps it somewhere on the 6536/7/8 side; the 6533 PFI is labeled REQ/PAUSE, so I take this to mean that corresponds to the REQ line on which the code was previously expecting the external clock.


Now, in NI-MAX, when I look at routes for the 6536, it appears that only 6536 PFI5 can be directly used as the digital input sample clock. Indeed, in Measurement Studio using NI-DAQmx 16.0, it appears that setting the sample clock source in my task's timing properties to PFI5 works but using any other PFI line causes an exception.


I am prepared to try, but have not yet tried, jumping 6533 PFI2 to 6536 PFI5 and attempting an acquisition using 6536 PFI5 as the digital input sample clock. Based on my understanding, this should work.



1. Does the above line of reasoning sound correct?

2. I see in NI-MAX it looks possible to create a route from one 6536 PFI line to another. Is it possible to, for instance, create a route from 6536 PFI2 to 6536 PFI5, jump 6533 PFI2 to 6536 PFI2 and then use 6536 PFI5 as the digital input sample clock (would it get the signal from 6533 PFI2)?

2.a. If so, how is that done? If not, how should I interpret the route table in NI-MAX?

2.b. What happens if I have, for instance, 6533 PFI5 physically jumped to 6536 PFI5, but a logical route created from 6536 PFI2 to 6536 PFI5 as per 2.a., and there's some signal being put onto 6533 PFI5? Does reading 6536 PFI5 give me a combined reading of 6533 PFI5 and 6533 PFI2, or do I get one or the other (which one)?

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Do you have a link to the user guide configuration diagram you mention?

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