Chapter 6 Symbol Variables *4. A symbol in a function block has a special significance. Please refer to chapter 7- Function Block and Library for more information. *5. For example, X0.0 and Y0.1 are bits in the word devices X and Y. Please refer to appendix B for more information. 6.1.5 Indirect Assignment and Modification for Register Symbol Variable In ISPSoft, a symbol can be modified by an index register. The format is Identifier@Index register . An index register can be an E device, an F device, or a symbol to which an E device or an F device is assigned. The data stored in an index register indicates the offset for an object modified. Take the figure above for example.
If the value in the index register E0 is 2, VAR_0@E0 indicates that 2 is added to the device address (D100) assigned to VAR_0, that is, VAR_0@E0 represents D102. When M0 is ON, the value 123 is transferred to the data register D102. The same rule applies to a symbol whose data type is ARRAY. The format is Identifier[Index]@Index register . The index must be a constant. If the index is a symbol, the symbol whose data type is ARRAY cannot be modified by the index register. In the figure below, Ary is an array composed of five elements, and the start device address is D200. When the system compiles the program, D200~D204 are assigned Ary. If the value in the index register E0 is 2, 6-17