Synchronizing the NI 9234 Module with NI 9225/9229/9233/9235/9236/9237/9239 Modules (FPGA Interface)

The NI 9225/9229/9233/9235/9236/9237/9239 module has a 12.8 MHz onboard oscillator, while the NI 9234 has a 13.1072 MHz onboard oscillator. All of these modules have delta-sigma ADCs that derive their sampling rates from the frequency of these onboard oscillators. An NI 9234 that uses its own 13.1072 MHz timebase can sample at a maximum rate of 51.2 kS/s (13.1072 MHz/256), while an NI 9225/9229/9233/9237/9239 that uses its own 12.8 MHz timebase can sample at a maximum rate of 50 kS/s (12.8 MHz/256), and an NI 9235/9236 that uses its own 12.8 MHz timebase can sample at a maximum rate of 10 kS/s (12.8 MHz/(256×5)).

Synchronizing the NI 9234 with the NI 9225/9229/9233/9235/9236/9237/9239 depends on the frequency of the shared master timebase. The NI 9234 can sample at a maximum rate of 51.2 kS/s when an NI 9234 is sourcing the master timebase. However, the NI 9234 can sample only at a maximum rate of 50 kS/s when an NI 9225/9229/9233/9235/9236/9237/9239 is sourcing the master timebase. It is important to note that when an NI 9235/9236 is sourcing the master timebase, the NI 9234 can still sample at a maximum rate of 50 kS/s. Furthermore, the NI 9225/9229/9233/9237/9239 can sample at a maximum rate of 50 kS/s when an NI 9225/9229/9233/9235/9236/9237/9239 is sourcing the master timebase. The NI 9235/9236 can sample at a maximum rate of 10 kS/s when an NI 9235/9236 is sourcing the master timebase. The possible sample rates of the NI 9225/9229/9233/9235/9236/9237/9239 change slightly when an NI 9234 is sourcing the master timebase. The NI 9225/9229/9233/9237/9239 can sample at a maximum rate of 51.2 kS/s when an NI 9234 is sourcing the master timebase, and the NI 9235/9236 can sample at a maximum rate of 10.24 kS/s when an NI 9234 is sourcing the master timebase.

The data rate in the C Series Module Properties dialog box automatically updates to reflect the actual data rate of the module when you change the master timebase source. However, the Data Rate property controls or constants on the block diagram do not automatically update when you change the master timebase source. Therefore, you might need to delete and recreate controls or constants for any Data Rate property on the block diagram after changing the master timebase source.

Refer to the NI 9xxx Operating Instructions and Specifications for the module for more information about understanding data rates. The latest versions of the operating instructions are online at ni.com/manuals.