Digital Output

The following table shows the correlation between terminology used for hardware functionality and for NI-DAQmx.

Table 3. Hardware and NI-DAQmx Terminology
Hardware Functionality NI-DAQmx Terminology
Open-drain Open collector
Push-pull Active drive

The default configuration of the NI USB-6501 DIO ports is open collector, allowing 5 V operation, with an onboard 4.7 kΩ pull-up resistor. An external, user-provided pull-up resistor can be added to increase the source current drive up to a 8.5 mA limit per line, as shown in the following figure.

Figure 6. Example of Connecting an External, User-Provided Resistor

1378

Additionally, you can configure the DIO ports as active drive. When configured as active drive, the total current sourced by all DO lines simultaneously should not exceed 65 mA.