Using PCI-1588 clock as reference for low frequency measurement with PCI-6251

[heinzchen]

I thought it would be possible to route the PCI-1588 onboard 10 MHz clock to RTSI and use it as reference clock for the PCI-6251's counters. Unfortunately the PCI-1588 seems not to support routing the onboard clock to RTSI (or anywhere else).

My second attempt was to generate an 1 MHz clock signal at RTSI 0 and use it as reference clock source. I have read a hundred times about the ability of M-series devices to use an external reference clock with its phase-lock loop, but I have never read that the external clock rate has to be 10 MHz or 20 MHz. So I was quite surprised that it is not possible to use the 1 MHz signal as reference.

I am at least able to wire the clock signal to the counter timebase source, but assuming that the PLL is not used then, I loose a lot of resolution with the 1 MHz timebase.

Have I missed something or this the only way to use the more accurate clock of the PCI-1588?

[mkais]

Dear Customer,

we've received an answer from our developer and the 1588 can't export its TCXO clk. The PFI lines can output clock signals <1MHz, but not its own internal oscillator.  

For this you need a routing module like the 6674t, 6653, etc.