Tasks

To improve the efficiency and distribution of the workload of the system UPC the PLC program control system can be divided into tasks with different execution properties.There are 2 categories of tasks available:one-shot execution simultaneous with the different types of system launchperiodically or cyclically repeated executionThe following tasks belong to the first categoryBOOT : run upon power-on of the target and subsequently at the PLC start command from GF Project VX CodeINIT : run after BOOT in the same BOOT conditions and also following full download from GF Project VX CodeINIT is the best task for correctly initialising the volatile variables of the PLC program because all the types of start for which it is invoked zeroed the non-retentive variables.Attention: the I/O management of the HW devices configured, whether installed on local bus or acquired through a fieldbus, is activated after running the INIT task when starting the user application program.The following tasks belong to the second categoryFAST: run periodically on the basis of times set for the system; it is run at the highest level of priority (HIGH); it hosts the update of the I/O.NORMAL: run every N configurable cycles of the FAST period; it is run at the medium level of priority (MEDIUM).SLOW: run every N configurable cycles of the FAST period; it is run at the low level of priority (LOW).BACKGROUND: run cyclically on itself with a suspension of 100 ms, not configurable; it is run at the lowest level of priority (LOWEST).Attention: the availability of the I/O of the HW devices configured, whether they are installed on local bus or acquired via a fieldbus, is not guaranteed the first time the above-listed tasks are run. The user program has to check through the interfaces prepared that this condition occurs according to the needs of the application (launch with partial availability of the I/O).