Hi Herman -
You have to explicitly tell the device to export its clock to the CLKOUT pin. The test panels in MAX don't provide this option, so you'll have to use a program in your preferred language to achieve this. There are several example programs provided with the NI-HSDIO driver. If you're using LV, you can run this one to export the clock:
Dynamic Generation with Exported Clocks.viYou'll also have to consider which pin you're trying to probe. The 6561 is a differential device, and its clock is exported to either LVDS or LVPECL outputs. If you're probing the LVDS pins (66/65), you'll need to provide a 100-Ohm termination instead of 50 Ohms. (See
http://www.national.com/appinfo/lvds/files/lvds_ch1.pdf) If you're probing the LVPECL pins, you'll need to consider proper termination for that standard, too.
David Staab, CLA
Staff Systems Engineer
National Instruments