Here is a tip about how to approach structured tags inside of Siemens’ WinCC V7.4 development environment. This also applies to WinCC Professional in TIA Portal as well.
When working with structured tags and picture windows, Siemens’ programming examples generally place the delimiter inside the picture window with the associated suffixes (see below left). This method is is more than sufficient when using native structure tags in WinCC; however, the tags can only be created using non-optimized memory and must all be stored in the same memory location (i.e. in the same data block).
An alternative approach recommended by AWC application engineers would be to place the delimiter OUTSIDE of the picture window and into the prefix (see below right). This method provides much greater flexibility because structured tags can now be created using a different delimiter. While WinCC does not allow the use of a period as a delimiter, underscores or other characters are available as options. In addition, placing the delimiter outside of the picture window allows the programmer to build a structured tag using information from multiple locations or sources(i.e. a PLC and a Modbus device, or two separate PLCs.) When the delimiter is moved to the prefix, it is abstracted away from the picture window so that the same picture window will work for both types of tags.
- Julyann Tu – AWC, Inc.