May Lee,
Route signal will not work to replace the 20MHz master timebase of the PCI-MIO-16-XE-50 with an external timebase. The only signal that can be routed to the Master Timebase of the 16-XE-50 is RTSI 7. The only signal that can be routed to RTSI 7 is the 20MHz Timebase. You may ask why that is. This allows several devices to be referenced to a common reference clock. For example, one device could be the master, and all the other boards in a system could use the same timebase as that board. This does not apply to your system, as there is no way to route an external signal to a master timebase. So, (1) is not an option.
In option (2), think of it as specifying an external scan clock. You are using your signal, but are dividing it down (by 10,000) to get a 1kHz signal from the 10MHz signal. To answer your first question, the source of counter 0 is an input on PFI 8, pin number 37 (on a 68-pin connection). Therefore, instead of using source on the block diagram, just use PFI 8.
To answer your second, you will need to divide it down, because you are actually inputting the scan rate.
Third, you can't use the 10MHz signal as the scan clock, because the frequency is too fast for your DAQ board. You can use it as the timebase for the scan clock by allowing the board to divide it down. The channel clock is going to be as fast as possible, with a 10 microsecond delay. In Traditional DAQ, you really don't need to worry about it.
This is the method I suggest. Use the alternative clock specification.
which clock = scan clock 1
clock frequency = -1
alternate clock rate specification
clock period = -1
timebase source = PFI pin, low to high
timebase signal = 8
timebase divisor = 10000 (if your signal is 10MHz, and you want a scan clock of 1kHz)
Remember to use AI Control instead of AI Start, and as an input to AI Read, make the time limit large enough so that you can acquire all your scans. I've included a .doc file below that shows (in very low resolution) what I simulated.
Thanks again for contacting National Instruments. Let me know if this resolves the issue,
Chad AE
Applications Engineer - National Instruments