I am using DAQmx to program PXI-6508 to communicate with perpheral device.
In normal situation, everything is OK. When PXI-6508 writes data to perpheral device, DAQmx sets OBF from high to low. After perpheral device detects OBF low, it sets ACK from high to low.
 
The problem is: 
If some errors occured during communication, ACK would never be set to low by perpheral device, therefore OBF will always be low. 
How can I set OBF from low to high?