Measurement Computing Data Translation DT3034 User Manual page 94

Principles of Operation
Error Conditions
DT3034 boards can report an output FIFO underflow error to the host computer. This error
indicates that the analog output data was not being transferred fast enough across the PCI bus
from the host computer to the output FIFO on the board.
If the D/A output clock occurs while the output FIFO is empty, an error is not reported since
the most likely cause is that the host computer has no more data to output; in this case, the last
value received from the host computer is output by the specified DACs continuously until the
board is powered down or new data becomes available. If, however, the host does an
additional write to the output FIFO (after the D/A output clock occurred while the output
FIFO was empty), the data is written to the DACs and the output FIFO Underflow error is
reported. This error has no effect on board operation; the host computer can clear this error.
To avoid this error, ensure that the host computer provides data to the output FIFO faster than
the DACs are converting the data. You can read the value of the output FIFO counter to
determine how many samples are in the output FIFO.
If this error condition occurs, the host computer stops transferring data to the board and the
board continues to output the last data transferred to it by the host computer.
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