Entry type: Manual, Entry ID: 92323076, Entry date: 05/13/2014
WinCC Professional V13.0
|Document:||WinCC Professional V13.0 (02/2014, English)|
|Type of topic:||Fact|
Only one user-defined function at a time is executed in Runtime. If several user-defined functions are waiting to be executed, they are lined up in a queue and executed one after the other.
A loop in a user-defined function therefore blocks the execution of the other functions in the queue even if the functions were initiated asynchronously.
WinCC supports a maximum nesting depth of eight user-defined functions. Note that the nesting depth is not checked.
If a user-defined function is configured for the "Runtime stop" event, the only system functions that may be used in this user-defined function are those which are available at the "Runtime stop" event.
Ensure that the ending of the Runtime is not interfered with by the execution of the user-defined function.
Configuration of user-defined functions
During configuration make sure that not too many user-defined functions are activated at the same time. Avoid a continuous system load of 100%.
User-defined functions are processed at a lower priority so as not to interfere with the display of values and operability. If system utilization is extreme, the user-defined functions to be executed are therefore first only reserved for execution. The maximum size of the reservation list is dependent on the HMI device and is limited by the maximum permitted number of user-defined functions. For additional information, see the performance features. If more user-defined functions are activated at one time than can be reserved, excess calls are discarded and a system alarm displayed.
HMI device changeover
If you use system functions in a customized function which are not available on the set HMI device, you get a warning. In addition, the corresponding system function in the user-defined function will be underlined with a wavy blue line.