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National Instruments Corporation
19
NI USB-6008/6009 User Guide and Specifications
I/O Protection
To protect the NI USB-6008/6009 against overvoltage, undervoltage, and overcurrent conditions, as
well as ESD events, you should avoid these fault conditions by using the following guidelines:
•
If you configure a DIO line as an output, do
not
connect it to any external signal source, ground
signal, or power supply.
•
If you configure a DIO line as an output, understand the current requirements of the load connected
to these signals. Do
not
exceed the specified current output limits of the DAQ device.
National Instruments has several signal conditioning solutions for digital applications requiring
high current drive.
•
If you configure a DIO line as an input, do
not
drive the line with voltages outside of its normal
operating range. The DIO lines have a smaller operating range than the AI signals.
•
Treat the DAQ device as you would treat any static-sensitive device. Always properly ground
yourself and the equipment when handling the DAQ device or connecting to it.
Power-On States
At system startup and reset, the hardware sets all DIO lines to high-impedance inputs. The DAQ device
does not drive the signal high or low. Each line has a weak pull-up resistor connected to it.
Static DIO
Each of the NI USB-6008/6009 DIO lines can be used as a static DI or DO line. You can use static DIO
lines to monitor or control digital signals. All samples of static DI lines and updates of DO lines are
software-timed.
PFI 0
PFI 0 is configurable as either a digital trigger input or an event counter input.
Using PFI 0 as a Digital Trigger
When an analog input task is defined, you can configure PFI 0 as a digital trigger input. When the digital
trigger is enabled, the AI task waits for a rising or falling edge on PFI 0 before starting the acquisition.
To use AI Start Trigger (ai/StartTrigger) with a digital source, specify PFI 0 as the source and select a
rising or falling edge.
Using PFI 0 as an Event Counter
You can configure PFI 0 as a source for counting digital edges. In this mode, falling-edge events are
counted using a 32-bit counter. For more information about event timing requirements, refer to the
