The information in the following section is intended for advanced users who develop custom I/O driver VIs using the LabVIEW FPGA Module.

The DAC internal registers are accessed through a serial interface port. The serial port can be configured to have a two-wire interface (clock and data in/out) or a three-wire interface (clock, data in, and data out). By default, the two-wire interface is selected; however, the PCI-5640R requires the DAC to be configured as a three-wire interface before any registers are read. Refer to the NI-5640R Examples for an illustration of how to configure a three-wire interface.
Caution Failure to initially configure the DAC as a three-wire interface may result in incorrect behavior.