ISPSoft User Manual 7.2.2 Symbol Variables in Function Block Function blocks are similar to POUs of the program type in that users can create local symbols in the function blocks. Local symbols can also be used in a function block. However, if local symbols are used in a function block in a project, the function block may not portable. If the function block is imported into another project, the project may not have the same global symbols. The following table describes the symbol variables related to function blocks and different categories of symbol variables supported by each PLC types. The category of symbol variables for function block:
7-6 Category Description AH/AS DVP AS5xx/ DVPxxMC VAR Only for function block arithmetic purpose internally. After executing, the symbol variable status is retained. VAR INPUT _ Used as input point of function block. The variable receives the assigned operand from the upper level POU (caller). When executing the function block, the operand value is copied into the function block. VAR OUTPUT _ Used as output point of function block. When finish executing the function block, the variable outputs the arithmetic result to the assigned operand by the upper level POU (caller). VAR IN OUT _ _ Feedback points of a function block.
When executing function blocks, use the point to send in the assigned operand content by the upper level POU (caller) to the function block. When finish executing the function block, arithmetic result feedback is output to the assigned operand by the upper level POU (caller). VAR RETAIN _ The retain variables can retain their value after power failure and the variable can be defined up to 15999 in total. VAR STATIC _ A static variable will be given a fixed address so as to share the same value across different instances using the same function block. VAR STATIC _ _ RETAIN Variables are declared as static and retained.