General-Purpose Inputs; General-Purpose Outputs; I/O For Fault Conditions - National Instruments PCI-8254R User Manual

Chapter 2 Hardware Overview

General-Purpose Inputs

The primary difference between general-purpose inputs and trigger inputs
is that you cannot use general-purpose inputs to initiate a timed pulse
generator. In an application, use the general-purpose inputs to get the status
of the inputs at a given point and not to synchronize the NI 8254R with an
external event.
An example of how to use general-purpose inputs is reading the status of a
general-purpose input as the first step in your inspection sequence and
recording that value as part of your inspection.

General-Purpose Outputs

The primary difference between general-purpose outputs and timed pulse
outputs is that the timing of general-purpose outputs is controlled by
software rather than hardware. As a result, timing of general-purpose
outputs changes as the inspection algorithm changes, which makes
general-purpose outputs less appropriate than timed outputs for camera
control, strobe light control, and other applications that require precise
timing.
An example of using general-purpose outputs is driving a relay that turns
on an Inspection in Progress light for an operator to see while the
inspection sequence is running.

I/O for Fault Conditions

The NI 8254R recognizes the following fault conditions:
•
•
In the event of a fault condition, the behavior of the NI 8254R is dependent
on configuration settings of the software-enabled Shutdown mode. To
resume operation, address the fault condition and cycle power on your
computer.
Table 2-4 summarizes how user configuration affects the behavior of the
NI 8254R in the event of a fault condition.
NI PCI-8254R User Manual
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External shutdown, when Shutdown mode is enabled
Watchdog timer expiration
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