The Six Flags
C (Communication): base flag, must be set for the CO to communicate at all. Without C, the CO is silent. R (Read): the CO responds to GroupValueRead requests with its current value. W (Write): the CO accepts GroupValueWrite telegrams from the bus. T (Transmit): the CO actively sends a GroupValueWrite telegram when its value changes. I (Initialise): on startup, the CO sends a GroupValueRead request to retrieve the current value.
Typical Combinations and Errors
Switch actuator command input (receives switch commands): C + W. Switch actuator status output (sends feedback): C + R + T. Push button output (sends button commands): C + T.
Common error 1: T flag missing on status CO → feedback does not arrive automatically, only on explicit read request. Common error 2: W flag set on sensor CO → sensor value can be overwritten from outside, leading to incorrect visualisations.
Key Facts
- C: communication active (always set)
- R: responds to read requests
- W: accepts write telegrams
- T: actively transmits on value change
- I: requests value on startup (read request)
- U: rarely used (update on feedback)