PCI-6251 Analog Output -- DAQ memory underflow error -200016

[rjohnson]

NI PCI-6251 DAQmx, AIMD-752 Motherboard, dual core processor, plenty of speed and ram, running WinXP Pro & LabWindows/CVI

keep getting DAQ memory underflow error -200016 when i attempt to generate an Analog Output signal with a rate above approx. 32,000 Samples/second (?!)

whats going on?  I've never seen this before.   Is this a problem with the motherboard?    This is even occuring on the CVI sample code "\Cont Gen Volt Wfm-Int Clk\ContGen-IntClk.cws"

has anyone had this problem, and is there a workaround?

thanks

PS:  full text of the message is this:

Measurements: Onboard device memory underflow. Because of system and/or bus-bandwidth limitations, the driver could not write data to the device fast enough to keep up with the device output rate.  Reduce your sample rate, alter the data transfer method (from interrupts to DMA), use a product with more onboard memory, or reduce the number of programs your computer is executing concurrently. Task Name: _unnamedTask<1>  Status Code: -200016
 

Message Edited by rjohnson on 07-16-2009 09:33 AM

[rjohnson]

correction:  Motherboard is AIMB-562

[rjohnson · Accepted solution]

Okay, found my answer.   For future reference, Olivia from NI Apps Engineering suggested that I change the data transfer mechanism per this Knowledge Base document:

http://digital.ni.com/public.nsf/websearch/C326F7D33CA6DB0E86256DFE008043B7?OpenDocument

... so i inserted the line of code between creating the AO channel and configuring the sample clock timing.

DAQmxCreateAOVoltageChan( ...

DAQmxSetAODataXferMech(TaskHandle,chan,DAQmx_Val_Interrupts);

DAQmxCfgSampClkTiming(...

now I'm able to generate output at a max sample rate of 2.35 MS/sec...  not quite the 2.86MS/sec stated in the 6251 specification, but close enough that I'll quit complaining

🙂