The YIELD function block interrupts a flow.
The flow voluntary gives away the program execution or other following tasks. As soon as the flow gains back its execution program, it will continue at that point. By interrupting a flow, the system gets the possibility to execute other flows and processes. Concurrent applications can be realized in this way.
If a backward loop is programmed without such an interruption, an endless loop is created which blocks any other activities.
The YIELD function block is active when the flow reaches this block and until it reaches the next stateful flow function block (either another YIELD or the END block).
The output Next has to be connected to the next flow chart function block. Otherwise the download to the target will be disrupted with an error message.
To understand the Flow Chart blocks better, you can have a look at our example Right use of Flow Chart blocks...
If the function block is active, the symbol will be colored green in online mode.
If the function block is not properly connected, it will be colored red in run mode.