Paul;
You can do that but keep in mind that will not replace the counter pulse train generation operation. I'm saying that because the counter will execute a hardware operation, and so, will be able to have a completely system independent operation, generating a nice and accurate TTL pulse train.
By doing that trough the analog output, as the data transfer in between the computer memory and the DAQ board is system dependent (since it uses DMA), you might have some glitches at the pulse train because of some delay caused by the data transfer. But that is definitely something to try out.
Hope this helps.
Filipe
