Vadi,
The first thing is to make sure that you have the latest version of NI-DAQ installed, NI-DAQ 6.9.1. If you need to install it, make sure you completely uninstall any prior versions. Then, you will have examples installed in either the NI-DAQ or the CVI directory. In the AO directory, you should find the WFMdoubleBuf example.
Start with that to make sure the output appears as you expect. Then, you can modify it to apply your external update clock, following the idea presented in the WFMsingleBufExtUpdate example. You might even want to double-check that your external clock acts as you expect using an oscilloscope.
Finally, modify the example such that you can update on multiple channels, remembering that you interleave each channels buffer into one buf
fer for WFM_DB_Transfer. Whatever data is in the buffer will be updated on the output channels.
Regards,
Geneva L.
Applications Engineer
National Instruments