Start and Sequence Multiple SFCs from PCS 7

To run SFC A.1 and then A.2, use a parent sequential control that issues each child's start request and waits for its documented completion state before advancing. For an operator-started parent, use the SFC's standard interface and supported SFC Visualization controls, or connect a custom WinCC request through the configured SFC external view. A DB bit is only an input request; it is not a substitute for the SFC's command/status interface.

Use the SFC interface rather than a raw internal DB

In SFC V9.0, each SFC has a standard interface for control in AUTO mode and operator control/monitoring in MANUAL mode. The manual describes an external view of an SFC chart in CFC so user-program control and status can be interconnected. For operator start from WinCC, make the SFC instance available for operator control and monitoring with the SFC Visualization add-on; a custom WinCC button should operate a deliberately exposed interface request, not write to undocumented internal chart data.

Coordinate child sequences from a parent SFC

For the order A.1 then A.2, implement a parent sequence with explicit steps and transitions: request start of A.1, wait until its documented completion/status output indicates finished, then request A.2, wait for completion, and finish. In SFC V9.0, the standard interface includes internal command input INTSTART and status output READY_TC (“finished ID”), while the SFC external view exposes the chart to CFC. Use the interface for the exact SFC chart/type implementation and version; do not assume a separate chart is automatically “called” by naming it A.1.

Create a WinCC start request safely

Configure the parent SFC instance's standard interface and operator-control availability according to the installed SFC manual. 2. If using the supported SFC Visualization faceplate, enable operator control for the instance and expose it on the OS. 3. If a custom WinCC button is required, connect its request through the SFC external view/standard interface in the approved AUTO/MANUAL mode; use the documented start command semantics and return/clear the request according to the interface behavior. 4. Prevent simultaneous or repeated requests from starting conflicting sequences; define behavior for active, completed, held, and faulted states. 5. In the parent chart, use completion/status and interlocks to advance from A.1 to A.2 only when the child sequence is complete.

Use sequencer start conditions for branches within one SFC

SFC sequencers are state/event-triggered sub-sequences controlled by start conditions. The SFC V9.0 manual permits up to eight sequencers in an SFC chart and up to 32 in an SFC type. Use this mechanism when the sub-sequences belong in one chart/type and their start conditions define the desired branching behavior. It is not automatically a call/return mechanism for two separate SFC charts.

Verification

Test the parent start request, the A.1 completion transition, A.2 start and completion, and every abort/hold/reset path. Check the SFC state and diagnostics as well as the external process signals. Confirm requests do not remain latched or trigger repeated starts and that the parent cannot advance while a child is still active.

Limitations and Operational Precautions

The ticket omits the PCS 7/SFC version, whether A.1 and A.2 are separate charts or sequencers, the SFC mode, and the attached diagram. Interface labels and behavior must be checked in the release-matched SFC manual. Simultaneous external/internal commands can produce an interconnection error; serialize control requests and do not download changes to a running process without approved testing and rollback.

Engineer FAQ

Can a DB bit start an SFC? It can serve as a request only when connected through a documented SFC interface/control design; do not write directly to undocumented internal DB data.

How can a WinCC operator start the parent SFC? Use the supported SFC Visualization faceplate with the instance enabled for operator control, or route a custom button through an explicitly configured interface.

How does the parent know A.1 is finished? Interconnect and evaluate the child SFC's documented completion/status output, such as READY_TC in the SFC V9.0 standard interface.

Are SFC sequencers the same as separate SFC charts? No. A chart/type can contain multiple sequencers with distinct start conditions; separate charts have separate external interfaces and execution states.

What must happen before A.2 starts? The parent's transition should require the A.1 completion condition and any required process permissives.

Technical References

SFC for SIMATIC S7 V9.0 Programming and Operating Manual, 05/2017, A5E41356228-AA; sections 5.5.3–5.5.4 (external view and control), 13.1 (standard interface including INTSTART/READY_TC), and 13.3 (sequencer start conditions).
CFC for SIMATIC S7 V9.0 SP5 manual, notes that the SFC external view replaces SFC_CTRL for CFC interconnections; verify this later CFC release detail against the installed SFC/CFC combination.