Didier,
I have paraphrased your question into English as: "How can I generate 8 non-periodic pulsetrains that are synchronized (referenced to the same t=0)?" Is this the correct question? If so, here are some possible answers:
1. With the 6602 alone, you can't. NI-DAQ hasn't implemented any buffered output capability. I love the 6602, but would love it more if it had this capability (and 2 others* -- further griping at bottom).
2. The "standard" NI solution would be to add a high-speed digital board such as the 6533 or 6534 to do such pattern generation. However, if you want to generate a 10 second pattern with 0.1 usec resolution, you'll need to generate 100 million patterns -- one for every 0.1 usec.
3. A better solution is offered by one of NI's Alliance partners, Viewpoint Systems. With their board, you only define the digital output pattern at the times when one of the bits changes. Then you can get 0.1 usec resolution (or better) with a much smaller buffer of digital output patterns. It's called the PCI DIO-64 and can be found in their website at www.viewpointusa.com
I personally used Viewpoint's earlier product, the ISA-based DIO 128, and was happy with the performance and support.
*3 gripes about the 6602
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A. If we can capture semi-periods into an input buffer, we should be able to then re-create that same pattern of transitions using a semi-period output buffer. Or, using a default for pulse width, the capability could be extended to buffered period output.
All the MIO boards make it possible to capture an analog input and then re-generate a facsimile as an output. There should be an analogous symmetry for counter pulsetrains.
B. We should be able to reset the count value to 0 (or a predefined preload value) on a hardware "trigger". This is presently supported only in encoder position measurement mode, only when the signal is hard-wired to the counter's default GATE terminal, and only if the SOURCE and AUX inputs match a specified pattern.
Example: capturing motion info from a stepper motor and encoder. For steppers based on step pulses and a digital direction bit, you can't force a hardware reset of the command position counter value simultaneous with the encoder counter.
C. Digital filterning should introduce only a phase lag artifact, not a resolution reduction too.
-Kevin Price
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