Chapter 6 Digital I/O
NI USB-621x User Manual 6-2 ni.com
Figure 6-1 shows the circuitry of one DI line and one DO line. The
following sections provide information about the various parts of the DIO
circuit.
Figure 6-1. USB-6210/6211/6215/6218 Digital I/O Circuitry
The DI terminals are named P0.<0..7> on the USB-6210/6211/6215/6218
device I/O connector. The DO terminals are named P1.<0..7> on the
USB-6210/6211/6215/6218 device I/O connector.
The voltage input and output levels and the current drive levels of the DIO
lines are listed in the NI USB-621x Specifications.
Static DIO on USB-6210/6211/6215/6218 Devices
You can use static DI and DO lines to monitor or control digital signals.
All samples of static DI lines and updates of DO lines are software-timed.
I/O Protection on USB-6210/6211/6215/6218 Devices
Each DI, DO, and PFI signal is protected against overvoltage,
undervoltage, and overcurrent conditions as well as ESD events. However,
you should avoid these fault conditions by following these guidelines:
•Do not connect a DO or PFI output lines to any external signal source,
ground signal, or power supply.
• Understand the current requirements of the load connected to DO or
PFI output signals. Do not exceed the specified current output limits of
the DAQ device. NI has several signal conditioning solutions for
digital applications requiring high current drive.
•Do not drive a DI or PFI input line with voltages outside of its normal
operating range. The PFI or DI lines have a smaller operating range
than the AI signals.
Static DI
I/O Protection
47 kΩ Pull-Down
P0.x
I/O Protection
47 kΩ Pull-Down
P1.x
Static DO
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