National Instruments NI VISION PCI-8254R 用户手册

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The following sections describe each fault condition.

Shutdown mode is a software-enabled feature that, when activated, allows 
an external device to halt the NI 8254R processing operations. 
Additionally, Shutdown mode allows you to specify user-defined 
shutdown states for all fault conditions.

When Shutdown mode is enabled and the shutdown input signal, 
ISO Input 11, turns off, the NI 8254R registers an external shutdown 
condition. When a fault occurs, outputs operate according to user-defined 
shutdown states. Each TTL output is configurable to drive high, drive low, 
or tri-state, and each isolated output is on/off configurable.

For prototyping when equipment is unavailable, you can wire from V to 

ISO Input 11 to simulate external equipment that indicates to the NI 8254R to operate 
normally.

The watchdog timer is a software configurable feature that can monitor 
software on the NI 8254R and take action if the software is unresponsive. 
The millisecond counter on the watchdog timer is configurable up to 
65,534 ms, in 1 ms increments, before it expires.

Configure the watchdog timer to take one of the following actions when it 
expires.

Table 2-4.  Fault Condition Behavior

External Shutdown

On

Off

Yes

No

Watchdog

On

Off

Yes

No