How Enter key handshaking works at runtime

When an object’s Enter button is pressed, the object writes a value to the data source. Use Enter key handshaking to hold the value at the data source for a specific period of time to ensure it is read before the operator sends a new value to the Value tag.
You can use Enter key handshaking with the Control list selector object.
How the handshaking controls and settings interact
When the operator presses the Enter button for an object that’s set up for handshaking:
  1. The Enter key control delay timer begins timing. When the time is up, the Enter tag is set to 1.
    If the Handshake reset type is Non-zero value, the Enter Handshake tag must be 0 when the Enter key control delay expires in order to set the Enter tag to 1.
  2. The Enter key handshake time and Enter key hold time timers begin timing.
  3. If the Enter Handshake tag is assigned, the Enter control remains set until the Enter key handshake time expires or until reset by the Enter Handshake tag, whichever happens first.
    If the Enter Handshake tag is not assigned, the Enter tag remains set until the Enter key hold time expires.
  4. The
    Enter
    control is reset to 0.
    TIP:
    If the
    Enter
    tag is not assigned, no handshaking takes place.
How the Handshake reset type works
The Enter Handshake tag resets the Enter tag:
  • Non-zero value
     resets the Enter tag to 0 when the Enter Handshake tag is a non-zero value.
  • Zero to non-zero transition
     resets the Enter tag to 0 when the Enter Handshake tag changes from 0 to a non-zero value.
In either case, if the Enter key handshake time expires before the Enter Handshake tag resets the Enter tag, the application reports an error to FactoryTalk Diagnostics.
Using objects in the graphic display
  • Before the Enter tag is reset to 0, the operator can provide input to other objects in the graphic display.
  • If the operator presses the Enter key for an object whose Enter tag has not yet been reset (using a key button or external keyboard or keypad), the application logs an error to FactoryTalk Diagnostics.
Graphic display changes
If the graphic display is closed, the Enter tag is reset to 0 and any handshake timing is also reset.
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