C135 PCS 7 (PCS7)
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Resolving SFC Type LiErr Faults and LI_ERR_STATE = 10 in SIMATIC PCS 7

Resolving SFC Type LiErr Faults and LI_ERR_STATE = 10 in SIMATIC PCS 7

In SIMATIC PCS 7 SFC Types, the fault 'LiErr' (Interconnection / Parameter Error) asserting with 'LI_ERR_STATE = 10' when switching from Manual to Automatic mode indicates a dual parameter limit violation. Decimal 10 corresponds to bitmask 16#0A (Bit 1 and Bit 3 asserted): Bit 1 indicates that the interconnected Control Strategy ('CS_LI') is below the minimum allowed limit (e.g., CS_LI = 0 when valid strategies start at 1), and Bit 3 indicates that an interconnected setpoint violates its configured high or low range. To resolve this, initialize 'CS_LI' with a valid non-zero strategy number and ensure all setpoint inputs are within defined operational boundaries.

Table of Contents

Executive Summary

When operating equipment phases and procedural sequences in SIMATIC PCS 7, switching an SFC Type from Manual (MAN) to Automatic (AUTO) mode triggers an automated parameter validation scan by the SFC runtime engine. If interconnected inputs fail validation, the block aborts the mode transition, raises the LiErr alarm, and populates the diagnostic error word LI_ERR_STATE. A frequent occurrence is error code LI_ERR_STATE = 10. This article decodes the bitmask structure of LI_ERR_STATE, explains why uninitialized strategy pins trip the fault, and provides the step-by-step resolution workflow.

Architecture and Fundamental Mechanics

SFC Type Parameter Validation and LI_ERR_STATE Bitmask Mechanics:

  • When Validation Occurs:
  • Whenever the SFC transitions from MAN to AUTO, or when a new control strategy / recipe setpoint is applied (QPARAM = 1), the SFC kernel executes a safety check across all interconnected parameters.
  • Decoding the LI_ERR_STATE Bitmask:
  • Decimal 10 = Binary 0000 1010 = Hex 16#0A (Bit 1 and Bit 3 asserted).
  • Bit 0 (16#01): Control Strategy high limit violated (CS_LI > CS_HL).
  • Bit 1 (16#02): Control Strategy low limit violated (CS_LI < CS_LL, typically CS_LI = 0 when strategies are configured $1\dots N$).
  • Bit 2 (16#04): Setpoint high limit violated (SP_LI > SP_HL).
  • Bit 3 (16#08): Setpoint low limit violated (SP_LI < SP_LL).
  • Why Error 10 Occurs:
  • If an engineer defined Control Strategies in the SFC Type (e.g., CS 1 and CS 2), but left input pin CS_LI floating or uninitialized at 0, Bit 1 trips.
  • Simultaneously, if an interconnected analog setpoint (e.g., Target_Temp_LI) is initialized at 0.0 while the parameter's minimum allowable range is configured as 20.0, Bit 3 trips.
  • Result: Bit 1 (2) + Bit 3 (8) = 10.

Step-by-Step Implementation Procedure

Diagnostic and Resolution Workflow for LI_ERR_STATE = 10:

  1. Identify the SFC Type Instance and Open CFC:
    - In SIMATIC Manager, locate the CFC chart containing the faulted SFC Type instance.
    - Open the chart in CFC Test Mode.
  2. Audit the Interconnected Control Strategy Pin (CS_LI):
    - Locate input pin CS_LI on the SFC block.
    - Check its current online value: if CS_LI = 0, it violates the low limit (CS_LL := 1).
    - Connect CS_LI to a valid strategy selector, or enter default value 1 on the pin.
  3. Audit Setpoint Parameter Ranges in SFC Characteristics:
    - Open the SFC Type in the Master Data Library -> open the SFC Editor.
    - In the Characteristics tree, expand Setpoints.
    - Review the configured Low Limit (LL) and High Limit (HL) for all setpoints.
    - Note any setpoints where the minimum limit is greater than 0.0 (e.g., Dosing_Rate_LL := 10.0).
  4. Correct CFC Setpoint Interconnections:
    - In the CFC chart, check the values feeding the corresponding ..._LI setpoint pins.
    - Ensure that initial values written to setpoint pins satisfy: LL <= SP_LI <= HL.
  5. Reset Fault and Switch to Auto Mode:
    - In WinCC Runtime, open the SFC faceplate.
    - Acknowledge alarms; verify LiErr clears from the faceplate banner.
    - Click the 'Auto' mode button; confirm the SFC transitions cleanly to Automatic mode without raising error 10.

Verification

To verify resolution of LiErr:
1. In CFC test mode, verify that SFC.LiErr = FALSE and SFC.LI_ERR_STATE = 0.
2. Switch the SFC faceplate from Manual to Auto mode; confirm the transition completes without error dialogs.
3. Force an invalid strategy value (CS_LI := 99); verify that LiErr asserts and LI_ERR_STATE immediately reports Bit 0 (1).

Limitations and Operational Precautions

Operational precautions:
- Never suppress LiErr monitoring by forcing internal flags; parameter checks prevent out-of-range recipe values from causing physical plant equipment damage.
- In recipe-controlled units (SIMATIC BATCH), verify that recipe formulas do not specify setpoints outside the SFC Type characteristic limits.
- If Control Strategies are not needed on the equipment unit, delete all strategy rows in Characteristics to permit single-sequence execution without CS validation.

Engineer FAQ

What does LiErr mean on an SFC Type?

LiErr stands for Linked Interconnection Error, asserted when interconnected parameters or control strategies violate allowable ranges.

What does LI_ERR_STATE = 10 mean?

Decimal 10 represents a bitmask of Bit 1 (Control Strategy low limit violated, e.g., CS=0) and Bit 3 (Setpoint low limit violated).

Why does LiErr appear only when switching to Auto mode?

Because parameter range checking across interconnected pins (_LI) is evaluated when transitioning into Automatic mode.

What happens if CS_LI is left unconnected in CFC?

It defaults to 0, which violates the minimum control strategy limit if strategies (1..N) are defined, tripping Bit 1.

Where are setpoint high and low limits defined?

In the SFC Type Characteristics editor under the 'Setpoints' folder.

Technical References

Related Articles

Related Tags

  • SFC Type Fault
  • LiErr
  • LI_ERR_STATE
  • Control Strategy Limits
  • Setpoint Validation
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