Program operation - execution of function blocks sequence

The function block diagram area contains the simulation and controller operation program. The program is created with the help of function blocks connected with each other by lines representing the exchange of information between blocks. It is very important to get acquainted with the rules of creating a program, because the correct operation of the created program depends on the knowledge of this subject.

ATTENTION: Incorrectly written program may contribute to unexpected or unforeseen behavior of the controller, which may cause a dangerous accident !!! Refer to the following rules for creating programs with function blocks in Simultus.

The compiler divides function blocks into two groups: A and B. Group A are blocks which order depends on the connections between the blocks. Group B are blocks that have no outputs or their outputs are not connected. The order in which these blocks are executed depends on their position in the diagram. First one to execute are the blocks that are higher. If the blocks of this group are on the same diagram level, the order of their execution depends on the distance from the left side, as shown in the figure below:

The diagram is divided into 4 parts placed in separate tabs:

The execution sequence of individual sections of the program is presented in the following diagrams:

The zero program cycle begins with the STARTUP section. It is only performed once. Then the CONTROL and PLC sections are executed cyclically.

If the controller operates in the simulation mode, then each cycle takes into account the order of the SIM section blocks according to the same principle described above. The controller block is treated as one of the function blocks of the SIM section, and the controller cycles are as shown in the diagram below.

The simulation cycle time is set in the 'Settings' tab under the 'Simulation' button:



In the dialog box, you can set the real time mode and the time interval between successive cycles (period):



Real time means that each cycle is run every specified period of time (set in the above window in microseconds).

No real time selection means that the next cycle will start right after the end of the previous one. In this situation, the simulation will run as fast as it can on a given computer.

While the simulation is running, it is possible to check the actual duration of the previous cycle by using the SYS_DATA function block from the 'Timers and counters' tab:





We suggest that you read the subchapter Main window, in which you can find a description of the most important menu items.