Latch behaviors and examples

The controller can detect "On" (rising edge) and "Off" (falling edge) pulses.
  • When a latch is enabled with the
    Rising
     edge configured, the controller monitors an "On" pulse.
  • When the latch is enabled with the
    Falling
     edge configured, the controller monitors an "Off" pulse.
Rising edge behavior
The input image is normally "Off" (0) and it changes to "On" (1) for one scan. The following section summarizes the events that occur when a latch input is enabled with a
Rising
 edge configured.
  • Upon detecting an external signal, the controller "latches" the event, but the input image remains "Off".
  • At the next input scan following the "latching event", the input image is turned "On".
  • The input image remains "On" for the next controller scan.
  • At the next input scan, after the scan in which the input image was turned "On", the input image is turned "Off".
IMPORTANT:
When an input is configured for the latching behavior, the input file value does not reflect the external input. When configured for the
Rising
 edge behavior, the input file value is normally "Off". When a rising edge pulse is detected, the input file value is "On" for one scan.
TIP: The gray area in the following examples represents the input filter delay.
Example 1: Rising edge behavior
Rising edge behavior
Rising edge behavior example1
Example 2: Rising edge behavior
Rising edge behavior
Rising edge behavior example2
Falling edge behaviors
The input image is normally "Off" (0) and it changes to "On" (1) for one scan. The following section summarizes the events that occur when a latch input is enabled with a
Falling
 edge configured.
  • Upon detecting an external signal, the controller "latches" the event, but the input image remains "On".
  • At the next input scan following the "latching event", the input image is turned "Off".
  • The input image remains "Off" for the next controller scan.
  • At the next input scan, after the scan in which the input image was turned "Off", the input image is turned "On".
IMPORTANT: When an input is configured for the latching behavior, the input file value does not reflect the external input. When configured for
Falling
 edge behavior, the input file value is normally "On" and changes to "Off" for one scan.
TIP: The gray area in the following examples represents the input filter delay.
Example 3: Falling edge behavior
Falling edge behavior
Example 3: Falling edge behavior
Example 4: Falling edge behavior
Falling edge behavior
Example 4: Falling edge behavior
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