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Chapter 2
Digital I/O
I/O Protection
Each DIO and PFI signal has limited protection against overvoltage, undervoltage, and
overcurrent conditions as well as ESD events. Avoid these fault conditions by following these
guidelines:
•
When configuring a PFI or DIO line as an output, do not connect it to any external signal
source, ground, or power supply.
•
When configuring a PFI or 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. NI has several signal conditioning solutions for digital applications requiring
high current drive.
•
When configuring a PFI or DIO line as an input, do not drive the line with voltages outside
of its normal operating range.
•
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.
DI Change Detection
The device can be configured to detect changes in the DIO signals, which includes Port 0 and
Port 1. Figure 2-12 shows a block diagram of the DIO change detection circuitry.
Figure 2-12.
DI Change Detection
S
ynch
S
ynch
P0.0
P1.7
En
ab
le
En
ab
le
En
ab
le
En
ab
le
Ch
a
nge Detection Event
