Справочник Пользователя для National Instruments NI 6509

© National Instruments Corporation

You can program the NI 6509 to send an interrupt when a change occurs on 
any input line.

The NI 6509 can monitor changes on selected input lines or on all input 
lines. It can monitor for rising edges (0 to 1), falling edges (1 to 0), or both. 
When an input change occurs, the NI 6509 generates an interrupt, and the 
NI-DAQ driver then notifies the software.

Excessive change detections can affect system performance. Use digital filtering to 

minimize the effects of noisy input lines.

The NI 6509 sends a change detection when any one of the changes occurs, 
but it does not report which line changed or if the line was rising or falling. 
After a change, you can read the input lines to determine the current line 
states. The maximum rate of change detection is determined by the 
software response time, which varies from system to system.

An overflow bit indicates that an additional rising or falling edge has been 
detected before the software could process the previous change.

Refer to the software documentation for information about how to set up 
and implement the change detection.

Table 2 shows a change detection example for six bits of one port.

Table 2.  Change Detection Example

—

—

yes

yes

yes

yes

no

no

yes

no

yes

yes

yes

yes

no

no

no

yes