How to Reset a Completed PCS 7 SFC Type to Idle in AUTO Mode

A PCS 7 SFC type that remains in Completed while operating in AUTO does not use the manual-mode SELFRESET behavior. Siemens' SFC interface documentation distinguishes SELFRESET, which returns Completed/Aborted/Stopped to Idle only in MANUAL, from the BOOL RESET input used as the automatic Reset command. For a version with that interface, apply the Reset command through the documented input and verify the sequence returns to Idle; confirm the installed SFC library/version and interlocks first.

Why Completed remains active

The source describes a sequence that reaches Completed in AUTO and returns to Idle when switched to HAND. Siemens SFC documentation specifies that SELFRESET automatically changes Completed, Aborted or Stopped to Idle only in MANUAL. The ticket's observed difference is consistent with that documented limitation; it does not indicate that AUTO mode itself is malfunctioning.

Use the automatic Reset interface

In the Siemens SFC for SIMATIC S7 V9.0 SP7 manual, the SFC interface lists RESET as a BOOL input for the automatic “Reset” command and ENRESET as the enable for Reset. SELFRESET is separately identified as applying only in MANUAL. The ticket reply identifies the same approach: use the RESET IN - BOOL AUTO command. Use the actual interface labels in the SFC version installed in the project.

Configure a controlled reset request

Open the SFC type/interface documentation matching the installed PCS 7 and SFC version. Confirm that RESET is an available BOOL input and that Reset is enabled through the applicable enable/interlock input.
Decide from the sequence design when a completed sequence is permitted to reset. Do not connect an unconditional reset that clears Completed before downstream logic or operators have consumed the completion state.
Generate the reset request according to the documented BOOL command behavior and project conventions. If it is driven by logic, make the request condition explicit and ensure the signal returns to its inactive state as required by the interface.
Compile and review the change through the site's engineering and safety processes before deployment.
In a suitable test environment, complete the sequence in AUTO, assert the approved Reset command, and observe the SFC state and outputs.

Expected state transition

When the reset request is accepted and enabled, the documented target state is Idle. Verify the displayed/current SFC state and relevant status outputs; do not assume a command was accepted just because the input changed. The sequence's process outputs and restart conditions must also be checked against the application's design.

Preserve the completion handshake

Automatically resetting immediately on completion can erase a state that batch logic, operator displays, interlocks or upstream/downstream coordination expects. If automatic return to Idle is required, define the handshake and the point at which reset may occur. A general-purpose timer or unconditional logic is not established by the source or manual and should not be invented as a universal implementation.

Verification

Test the sequence in a controlled environment using its actual AUTO mode and documented RESET input. Confirm the completion event is observed by dependent logic before reset, the reset is accepted, the SFC reaches Idle and no unintended step/action restarts. Check the applicable SFC version manual for edge/level handling and reset permissives.

Limitations and Operational Precautions

The ticket does not give the PCS 7/SFC version, SFC type configuration or sequence handshake. The cited manual is SFC for SIMATIC S7 V9.0 SP7; interface names and behavior must be checked against the installed release. Resetting a live sequence can affect process outputs and sequencing. Review the functional design and test before production use.

Engineer FAQ

Why does it return to Idle in HAND but not AUTO? The documented SELFRESET input applies only in MANUAL; AUTO uses the Reset command interface.

Which input is used for the automatic reset? The cited manual lists BOOL input RESET as the automatic Reset command and ENRESET as its enable.

Should RESET be held high continuously? The source does not specify signal timing. Follow the exact version's interface description and the project's command convention.

Can reset occur immediately when Completed goes true? Only if downstream logic and the process design no longer need the Completed indication; otherwise preserve a handshake.

Does an accepted reset prove the sequence is safe to restart? No. Check Idle state, outputs, permissives and process conditions before allowing a new start.

Technical References

Siemens, SFC for SIMATIC S7 V9.0 SP7 Programming and Operating Manual, SFC inputs/outputs including ENRESET, RESET and SELFRESET: https://support.industry.siemens.com/cs/attachments/109805980/s7sfcs7b_en-US.pdf