Digital I/O

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Synchronized TTL Output

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     I'm looking for a PXIe or PCIe card that can provide at least 8 TTL digital outputs. Any 4 of these TTL digital outputs will need to be synchronized in an arbitrary/programmable way (i.e., separated by specified delays). Need said delays to be programmable and accurate to within +/- 100nSec.  Anyone have an idea or a recommendation?



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Message 1 of 5

It may depend on the kind of TTL signals you plan to generate:

  • If you want pulses or pulse trains, you'll want a device with 4 counter/timers.
  • If you want 4 bits worth of arbitrary digital timing patterns, you'll want a device that supports hw-clocked DIO at 10 MHz.

There are X-series boards that meet both of those, though some of the lower-cost models only support 1 MHz DIO.  (The timing *accuracy* would still be better than +/- 100 nanosec, just not the timing *resolution*).



-Kevin P

Message 2 of 5

Hi Kevin,


     Thanks for the response.  I think I am looking for "4 bits worth of arbitrary digital timing patterns".  At this point, a 10MHz clock rate is a nice to have; but I think 1MHz would suffice.  So, I think the NI PCI-6220 might work for us; but if not, the NI PCI-6250 would.  The support pages for those devices recommend considering the 6320 X-series and 6351 X-series respectively.  However, I do not see it specified that those devices offer correlated DIO.  Do they?  Also, I may need to have this in a PXI form factor and don't see any PXI cards specified as having correlated DIO.  Please advise further if you can.




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Accepted by topic author Billy_Barty

The "Correlated DIO" feature found in M-series boards (model #'s 62xx) was kinda like having both a badly sprained ankle and crutches.  Port 0 supported the possibility of hw-clocking, but the board couldn't derive such a clock internally the way it does for AI and AO tasks.  You had to supply the timing source from somewhere else.


X-series boards (model #'s 63xx) still support that same "correlated" usage, but don't publicize it because the design included internal clocking support for DIO -- like a fully functional ankle with no *need* for crutches.  The specs now simply refer to the supported sample clock frequency.


There are several X-series PXI-express boards you could consider with model #'s starting PXIe-63__.  Note that you need to have a chassis that supports PXI-express.  If you're stuck with an older PXI chassis, you'll be limited to using an M-series board with correlated DIO.  This may lead you to use 1 or 2 (of 2 total) counters to generate a sample clock for your DO task.



-Kevin P


P.S.  There may well be a dedicated digital-only board that would work out well too, I just don't have enough familiarity to offer advice.

Message 4 of 5

Hi Kevin,


     The PXIe-6341 looks like the lowest cost alternative that might work for us but only offers a 1MHz clock rate for the DIO lines.  Next in cost is the PXIe-6535 (which I looked up based on your P.S.); it is DIO only (which is all we really need) but offers a 10MHz clock rate.  Then there is the PXIe-6361.  It too offers a 10MHz clock rate for the DIO lines; but like the PXIe-6341, it has all the analog and counter/timer features that I don't really need and is the priciest of the 3.

     At any rate, looks like I have 3 alternatives I can propose.  Thanks again.



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