# How Enter key handshaking works at run time

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 object overwrites the value.

You can use Enter key handshaking with these objects:

- String input enable button
- Control list selector
- Numeric input enable button
- Numeric input cursor point

## Use objects in the graphic display

- Before the Enter connection is reset to 0, the operator can provide input to other objects in the graphic display.
- If the operator presses the Enter key (using a key button or external keyboard or keypad) for an object whose Enter connection has not yet been reset , the application logs an error.

## Graphic display changes

If the graphic display is closed, the Enter connection is reset to 0 and any handshake timing is also reset. In effect, the handshaking is canceled.

## To set up an object for handshaking

Enter key handshaking works by setting the object's Enter connection to 1. Until the Enter connection is reset to 0, no new values can be sent to the Value connection.

There are two ways of using Enter key handshaking:

- Hold the value at the data source for a specified period of time,
- Hold the value at the data source until the data source notifies FactoryTalk View that the value has been read.

## See also

Hold a value for a specified length of time

Hold a value until it is acknowledged

Causes of run-time errors for Enter key handshaking