You can configure the digital voltage of the USB-6451 by selecting logic families on the USB-6451. The logic family configuration affects the digital input, digital output, counter input, counter output, and trigger functions.

Logic families are groups of logic circuits with standardized voltage levels that constitute a valid logic state.

The USB-6451 supports four logic families. The USB-6451 is configured to 5 V by default.

Table 23. USB-6451 Logic Families
Logic Family Description
1.8 V Compatible with 1.8 V CMOS signals
2.5 V Compatible with 2.5 V CMOS signals
3.3 V Compatible with LVTTL signals
5 V Compatible with TTL and 5 V CMOS signals

Configuring the Logic Family

  1. Add the DAQmx Physical Property node to your block diagram.
    The DAQmx Physical Property node is located on the DAQmx Constants & Property Nodes palette under Measurement I/ODAQmx - Data AcquisitionDAQmx AdvancedDAQmx Constants & Property Nodes.
  2. Set the ActivePhysicalChans property to show digital input channels.
    1. Right-click the ActivePhysicalChans and select Create » Constant to add a constant.
    2. Right-click the constant and select I/O Name Filters.
    3. In the Filter Names dialog box, set I/O Type to Digital Input or Digital Output and Port/Line Filtering to Ports Only.
    4. Click OK.
    5. Set the constant to Device Name/port0, where Device Name represents the name of your device.
  3. Select Digital » Port Logic Family to add the Dig.PortLogicFamily property node.
  4. Right-click the Dig.PortLogicFamily and select Create » Constant to add a constant.
  5. Select a logic family on the constant.