One method of using Enter key handshaking is to hold the value at the data source until the data source notifies the application that the value has been read. To do this, specify the Enter key handshake time and a Handshake reset type. Enter key control delay is optional.
As long as the Enter connection is set to 1, the user cannot send new values to the Value connection.
How the Enter Handshake connection resets the Enter connection depends on which Handshake reset type you select:
Non-zero value resets the Enter connection from 1 to 0 when the Enter Handshake connection has a non-zero value.
Tip: |
If the "Handshake reset type" is "Non-zero value," the Enter handshake connection must be 0 when the "Enter key control delay" expires to set the Enter connection to 1. If the Enter handshake connection already has a non-zero value, the assumption is that the Enter connection is still set to 1 from a previous event. Then the Enter connection is not set to 1 and Enter key handshaking does not happen. |
Zero to non-zero transition resets the Enter connection when the Enter Handshake connection changes from 0 to a non-zero value.
In either case, if the "Enter key handshake time" expires before the Enter Handshake connection resets the Enter connection, the Enter connection is reset to 0 and the application reports an error to diagnostics.
How Enter key handshaking works at run time