SIMATIC S7 CFC (Continuous Function Chart) -
Interconnection instead of programming

The CFC engineering tool (Continuous Function Chart) is available as a STEP 7 option, particularly for technologists who also configure the user program of the plant. CFC permits techno­logical requirements to be trans­formed into executable automation programs with minimal outlay. To do this, predefined blocks must simply be connected to each other and then parameterized. Extensive programming experience is not required.

Function
Technology functions are only parameterized by linking function blocks (e.g. AND, OR, PID controllers, limiting functions, etc.). Time-consuming program­ming is not necessary. Creating programs by linking standard blocks is faster and less error prone than conventional programming. Function blocks created with other STEP 7 programming languages can also be integrated. Executable code is generated more or less at the press of a button and transferred online to the programmable controller.
The configuration interface is a type of graphical drawing interface onto which predefined blocks are placed and connected with each other according to technological rules. Only the connections to be linked need to be marked. The CFC editor automatically determines the path to be followed by the lines and composes the lines (even across the boundaries of the page/chart).

The following structure elements increase clarity:

• Hierarchical CFC charts (chart-within-a-chart technique):
  Other CFC charts can be integrated into a CFC chart.
  Integrated charts can be changed without affecting the inserted sections.
• Creation of block types:
  Centrally created blocks can be changed centrally and can be reused anywhere.
• Extending the chart size through subcharts (up to 26 subcharts are possible)

CFC fulfills increased requirements during operation:

• Delta online loading is supported. Changes to the configuration are loaded in the CPU state "RUN-P".
• The program sequence can be influenced:
  Currently measured values can be easily overwritten online by the user.

Block library
CFC is supplied with a library of predefined blocks for essential functions:

• Elementary blocks: e.g. arithmetic blocks (sine, cosine, tangent, etc.), AND & OR functions, subtracting, multiplying, .....
• Blocks for SIMATIC S7-300 and S7-400: e.g. controller blocks, clock generators, counter blocks, timer blocks, .

In addition, blocks from STEP 7, PCS 7 or D7-SYS, for example, can also be linked and parameterized. Furthermore, custom blocks can be created and managed in libraries.