Hi jmoses,
The FIFO on the 4461 is actually 1023* samples (found in the specs page).
The 4431 doesn't actually list a FIFO size in the specs page, but any device which supports hardware-timed output is going to have some sort of FIFO to avoid running out of data to generate. Using the Output.OnBrdBufferSize property node returns 4095* samples--it makes sense this FIFO would need to be larger given the higher latency of USB transfers. Unless you're using on-board regeneration, the FIFO size shouldn't typically be a concern since it is designed to be large enough to accomodate continuous generation at the full specced rate of the device.
Corrective Action Request number 149512 has been filed concerning the issue of the missing documentation on our USB DSA devices--I apologize for any inconvenience.
*If you're interested, the reason that the FIFO is not an even number of samples is that the software limits the buffer size to one less than the actual hardware buffer. This is required for us to be able to detect the difference between a FIFO empty and a FIFO full state (we use a Read and a Write pointer to handle the transfers of data in and out of the FIFO--we can tell that the buffer is empty when the two pointers are equal, and full when the Write pointer is one sample behind the Read pointer).
Best Regards,
John
John Passiak
