Glossary · PLC and control programming
Continuous function chart (CFC)
Also known as: CFC editor
German: Continuous Function Chart (CFC)
In PLC and process control programming, a continuous function chart (CFC) is a graphical language in which function blocks are placed freely on a sheet and connected by signal lines, with an explicit or automatically determined execution order.
- PLC programming
- Process industry
In one sentence
CFC is a graphical programming language that places function blocks freely on a chart and connects them, common in process control.
Example
In a DCS project, a temperature control loop is built in CFC by connecting an analog input block, a PID block and an analog output block on one chart.
How it applies
- Engineering: CFC is widespread in process control systems and in several IEC 61131-3 environments as an additional editor. Engineers build control loops, interlocks and monitoring logic by wiring block instances together, which mirrors the P&ID and the loop diagram.
- Commissioning: The execution order of blocks matters for signal timing. Engineers check whether the tool sorts blocks automatically or whether the order is set manually, and verify it for loops with feedback paths.
- Maintenance: Online views of a CFC show live values on the connections, which helps technicians follow a signal from sensor to actuator.
- Documentation: Chart printouts are often part of the software documentation. Add chart names, a short purpose statement and cross-references to the loop tag numbers, so that the charts can be matched to the P&ID.
CFC vs. FBD
The Function block diagram (FBD) of IEC 61131-3 arranges blocks in networks that are executed in order from top to bottom. CFC lets blocks sit anywhere on a sheet and needs a defined execution order. CFC is not one of the languages defined in IEC 61131-3 itself; its availability and details depend on the engineering tool.