How to Reset a PCS 7 SFC from Completed to Idle in AUTO

An SFC that reaches Completed in AUTO stays there unless its configured runtime behavior or program issues a state-changing command. The RESET input is the documented automatic Reset command; SELFRESET returns Completed, Aborted or Stopped to Idle only in MANUAL. For an automatic return to Idle in AUTO, condition a reset request on the intended completion state and process permissives, then verify the transition on the specific chart or type.

Why an SFC Remains Completed in AUTO

The PCS 7 SFC V9.0 SP1 manual describes SELFRESET as an automatic transition from Completed, Aborted or Stopped to Idle only in MANUAL. Cyclic operation behaves differently: it resumes in Starting after Completed. With cyclic operation off, an SFC remains Completed unless a command exits that state.

Use the Automatic Reset Input

The standard interface provides RESET as an automatic Reset command (BOOL, default 0) and ENRESET as its enable (BOOL, default 1). In AUTO, program logic controls execution through the SFC inputs/interconnections.

Identify whether the logic is an SFC chart, type or instance, and confirm its interface/version.
Determine the completion indication and process conditions that must be satisfied before reset.
Drive the documented RESET input from a bounded project-approved condition when the sequence is complete and ready to return to Idle. Confirm ENRESET permits the command; do not leave reset unconditionally asserted.
Test in an approved offline or commissioning setup and verify the SFC returns to Idle and downstream logic sees the expected state.
Apply operating-system changes only through site change control and the approved download procedure.

Choose the Intended Post-Completion Behavior

Use SELFRESET for the documented automatic reset in MANUAL. Use cyclic operation when the intended next state is Starting. Use RESET when the required destination is Idle in AUTO, subject to state logic and project-specific permissives. Do not change mode solely to obtain Idle if the process requires AUTO.

Verification

Monitor the state before and after the reset request. Verify the request is made only in the intended state, ENRESET is true, and the state output reaches Idle. Confirm step actions, interlocks and external sequencing leave the process in a safe expected state.

Limitations and Operational Precautions

The ticket does not identify PCS 7/SFC version, chart versus type, step logic, interlocks, or whether reset should occur immediately on completion. Confirm documentation applicability to the installed version and SFC. Resetting can change process state and permit a subsequent start. Define the condition with the process engineer and validate it before download.

Engineer FAQ

Does SELFRESET return an AUTO SFC to Idle? No. Siemens documents this option for MANUAL mode only.

What is RESET? The standard interface's automatic Reset command input, a BOOL with default 0 in the cited V9.0 SP1 documentation.

Does cyclic operation return to Idle? No. It resumes in Starting after Completed.

How can a program detect completion? Use the documented COMPLETED output or the appropriate version's SFC_STATE indication.

Should RESET remain high? Do not assume so. Use a bounded command consistent with the project's state logic and verify it does not repeatedly affect later states.

Technical References

Siemens, SFC for SIMATIC S7 (V9.0 SP1) Programming and Operating Manual, 10/2017, §§13.1–13.3 (standard interface, RESET, ENRESET, SELFRESET), §16.2.4 (cyclic operation), §16.2.5 (operating states): https://cache.industry.siemens.com/dl/files/020/109755020/att_939593/v1/s7sfcs7b_en-US.pdf
Siemens, SFC for SIMATIC S7 (V9.0) Programming and Operating Manual, §13.3 (state encoding): https://cache.industry.siemens.com/dl/files/747/109748747/att_924279/v1/s7sfcs7b_en-US.pdf