"Data was overwritten before it could be read by the system" Counting with PCI 6601 with 20MHz clock

[IUCHEM]

I am running the example "Count digital events-buffered-external clock-continuous" In the porcess of trying to debug another application thaty I wrote. 

I want to use this example to count ttl pulses on a counter input on PCI 6601but I want to 20Mhz clock that is on the DAQ card PCI 6601, But if I do this, I get the following error: 

"Data was overwritten before it could be read by the system

If Data Transfer Mechanism is Interrupts, try using DMA or USB Bulk. Otherwise, divide the input signal before taking the measurement."

I used sample frequency of 20MHz as suggested, and I used single channel single sample mode. 

Could someone help me explain the error message and what may be wrong? 

I appreciate any help.

Thanks

Aditi 

[IUCHEM]

I am running the example "Count digital events-buffered-external clock-continuous" In the porcess of trying to debug another application thaty I wrote. 

I want to use this example to count ttl pulses on a counter input on PCI 6601but I want to 20Mhz clock that is on the DAQ card PCI 6601, But if I do this, I get the following error: 

"Data was overwritten before it could be read by the system

If Data Transfer Mechanism is Interrupts, try using DMA or USB Bulk. Otherwise, divide the input signal before taking the measurement."

I used sample frequency of 20MHz as suggested, and I used single channel single sample mode. 

Could someone help me explain the error message and what may be wrong? 

I appreciate any help.

Thanks

Aditi 

[Michael-B · Accepted solution]

Hello Aditi,

What exactly is the purpose of using the 20 MHz clock?  Are you counting the edges of it? 

You could try using the "DAQmx Configure Input Buffer" VI to increase the size of your buffer.  You could also use DAQmx Channel Node to set the data transfer mechanism to DMA.  If you create a channel node, you can get to that specific property via this path: Counter Input:General Properties:More:Advanced:Data Transfer and Memory:Data Transfer Mechanism Property.