National Instruments NI VISION PCI-8254R 用户手册

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.

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.

The NI 8254R recognizes the following fault conditions:

•

External shutdown, when Shutdown mode is enabled

•

Watchdog timer expiration

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.