Chapter 7 Function Block and Library If a symbol whose data type is general data type is declared, a device is assigned to the symbol when the program is compiled. Likewise, if a symbol whose data type is a function block is declared, a corresponding function block instance is produced when the program is compiled. Besides, the number of function block definitions which produce the instances in a project for an AH5X0 series CPU module can not be larger than 1024.
(The function block definitions which do not produce the instances are not included.) If a symbol with a general data type is declared, a device will be assigned to the symbol when the program is corresponding function block instance will be produced, whenever a program is compiled. However for an compiled. Likewise, whether it will be used or not, if a symbol with a function block data type is declared, a AH5X0 series CPU module, the number of function block instances as POUs in a project cannot exceed 1024.
(The function block definitions which do not produce instances are not included.) This limitation only applies to AH5X0 series; for other series, the number of function block definitions can be as large as the size of the PLC internal memory. In sum, the operation of a function block involves a definition and an instance. Function block definitions are related to planning, and function block instances are related to execution. Take products for example. A function block definition is the same as the product specifications developed by engineers, and a function block instance is the same as the product produced according to the specifications.
7.2.6 Calling Relation Between Function Blocks In ISPSoft function block specification, a function block can call another function block. For AH series, maximum of 32 layers can be called; AS/DVP series, a maximum of 16 layers can be called; DVPxxMC/ AS5xx series, there are no limits on calls. To identify, the function block example called by POU is defined as the first layer. The program in function block A calls function block B, and the program in function block B calls function block C. In other words, function block A is superior to function block B and function block C, and function block B is superior to function block C. In ISPSoft, a function block is not allowed to call itself.
As a result, if function block 7-21