# How the control list selector works at run time

At run time the control list selector is highlighted to show the state with a value that matches the Value connection value at the data source. The operator can scroll through the list to select a different state. The value assigned to the selected state is written to the Value connection.

## Scroll through the list

- The operator can scroll and select states and write out the value associated with the selected state using key buttons or by using the arrow keys and Enter key on a keypad or an external keyboard.
- The list scrolls if it contains more states than can be viewed at one time. When the operator reaches the bottom of the list and presses the Move Down button, the cursor moves to the top of the list. If the cursor is at the top of the list and the operator presses the Move Up button, the cursor moves to the bottom of the list.
- If "Write on enter" is selected (on the General tab), the value is not sent to the Value connection until the operator presses the Enter button or Enter key. If "Write on enter" is not selected, the value is sent as soon as the operator scrolls to a different state.

  Tip: | In the control list selector, when you scroll to a state and select it, it takes a specific period of time for the system to write the value and make the state selected.

## Use auto repeat

If auto repeat is set up for the key button (on the key button's Timing tab) and the operator holds down the Move Up or Move Down button for the specified Auto repeat delay time, the list begins to scroll. If "Write on enter" is not selected, the application attempts to send a value to the Value connection for each state that scrolls by. However, some values may be lost if the Auto repeat rate is too fast for all the values to register.

## Open graphic displays

When you open a display at run time, the application reads the Value connection value and highlights the state with the matching value. If no state matches the Value connection value, no state is highlighted and the cursor appears at the top of the list.

## Update the list once the display is open

The application periodically reads the Value connection and highlights the state with the matching value. If no state matches the Value connection value, no state is highlighted and the cursor remains beside the previously highlighted state.

The frequency with which the application updates the control list selector depends on the update rate for the tag assigned to the Value connection.

## Invalid values

When the operator moves to a new state that has an invalid value and presses Enter, the cursor moves but the state is not highlighted.

## See also

Causes of run-time errors for the control list selector

Set up connections for the control list selector

How Enter key handshaking works at run time