Resolving Module Driver Generation Errors for F_CH_AI and F_CH_DI in SIMATIC PCS 7

In SIMATIC PCS 7 S7 F-Systems, driver generation errors for fail-safe channel blocks (F_CH_AI, F_CH_DI)—such as 'module not configured' or compiler driver aborts following I/O address reassignments—occur when channel address parameters (CHADDR, CH_INF) retain orphaned pointers to obsolete hardware configurations. Resolving driver failures requires saving and compiling HW Config, clearing broken pin connections, and re-running the module driver generator to reconstruct fail-safe diagnostic links.

Role of Fail-Safe Channel Drivers in S7 F-Systems

In SIMATIC PCS 7 safety-instrumented systems (SIS) running S7 F-Systems:
* Safety signals from fail-safe electronic modules (such as ET 200M/ET 200SP HA F-AI $8 imes ext{I}$ or F-DI $16 imes24 ext{VDC}$) are processed by dedicated fail-safe channel driver blocks.
* F_CH_AI: Processes analog safety signals (4–20 mA SIL 3 inputs).
* F_CH_DI: Processes discrete safety signals (E-Stop, door switches, burner permissives).
* Unlike standard APL drivers, fail-safe channel blocks evaluate PROFIsafe communication headers, safety CRC checksums, discrepancy times, and sensor passivation states.

Mechanics of the PCS 7 Module Driver Generator (Generate Module Drivers)

When an engineer compiles CFC charts with Generate module drivers enabled:
1. The compiler queries the hardware configuration database to identify the physical F-module corresponding to the address connected to F_CH_AI.VALUE or F_CH_DI.VALUE.
2. It automatically creates system diagnostic blocks: F_MOD_x (fail-safe module diagnostic block) and F_PS_x (PROFIsafe communication supervisor).
3. It interconnects the diagnostic outputs to the channel driver parameters:
* CHADDR / CHADDR_R: Channel logical address in the process image.
* CH_INF / CH_INF_R: Channel diagnostic information structure.
* MOD_INF: Module state pointer.

Root Causes: Address Reassignment and Parameter Desynchronization

When an engineer reassigns I/O addresses in HW Config (e.g., shifting an F-AI card from PIW 512 to PIW 600) and subsequently adds F_CH_DI or recompiles charts:
* The Compilation Abort: The driver generator encounters outdated values stored in the instance parameters CHADDR or CH_INF. If the hardware database no longer contains a safety module at the old address, the compiler cannot resolve the hardware pointer and aborts with:

Module not configured or parameter value is not supplied.
* Uncompiled HW Config: If address modifications in HW Config were saved but not compiled, the internal hardware description database remains out of sync with the CFC chart addresses.

Step-by-Step Procedure to Resolve F_CH_AI and F_CH_DI Generation Faults

To restore clean driver generation:
1. Save and Compile HW Config:
* Open STEP 7 HW Config for the target AS.
* Select Station -> Save and Compile. Confirm that hardware compilation finishes with 0 errors.
2. Reconcile Signal Address in CFC:
* Open the CFC chart containing F_CH_AI or F_CH_DI.
* Double-click the input pin connected to the field address (VALUE pin).
* Confirm that the address matches the exact logical input address configured in HW Config (e.g., IW 600).
3. Purge Corrupted Driver Interconnections:
* Right-click the channel block and select Delete Interconnections -> To System Drivers.
* Alternatively, delete the problematic F_CH_AI block and re-insert a clean instance from the S7 F-Systems library.
* Reconnect the raw I/O symbol to the VALUE input pin.
4. Execute Full Driver Generation:
* In SIMATIC Manager, select the Chart folder.
* Select PLC -> Compile and Download Objects (or open CFC and select Chart -> Compile -> Changes Only).
* Ensure the checkbox Generate module drivers is checked.
* The compiler scans the clean hardware database, generates matching F_MOD_x blocks, and parameterizes CHADDR and CH_INF without errors.

Verification

Confirm that CFC compilation finishes with 0 Errors, 0 Warnings.
Open the system chart generated by the compiler (e.g., @2(1)): verify that the fail-safe module diagnostic block (F_MOD_x) is present and interconnected to F_CH_AI.
Download changes to the Automation Station in RUN mode.
In CFC dynamic test mode, verify that F_CH_AI.QBAD = 0 (Quality Good) and F_CH_AI.V = live process value.
Disconnect the analog input wire in the field: verify that QBAD = 1 and PASS_OUT = 1 (Channel Passivated).

Limitations and Operational Precautions

Modifying safety I/O configurations or safety program signatures alters the F-Signature of the safety program, requiring recalculation and safety acceptance sign-off.
In PCS 7 V9.1 SP2 / V9.2 environments, ensure the installed S7 F-Systems library version matches the PCS 7 compatibility matrix.
Never manually write to parameters managed by the driver generator (CHADDR, CH_INF), as manual overrides are destroyed during the next compilation.

Engineer FAQ

What is the purpose of F_CH_AI in PCS 7?
It serves as the fail-safe analog input channel driver in S7 F-Systems, managing safety scaling, passivation, and PROFIsafe diagnostics.
Why does the driver generator report 'Module not configured'?
The hardware configuration was not compiled after address modification, or the address connected in CFC does not exist in HW Config.
How do I force PCS 7 to rebuild all system drivers from scratch?
Delete the system charts (names beginning with @) and compile the program with 'Generate module drivers' enabled.
Does modifying F_CH_AI addresses change the safety program CRC?
Yes, modifying safety block parameters alters the collective safety CRC signature of the F-runtime group.
What block supervises the physical fail-safe hardware module?
The fail-safe module diagnostic block F_MOD_x generated automatically by the driver generator.
Can standard APL channel drivers (Pcs7AnIn) be used with fail-safe cards?
Standard channel drivers can read F-cards in non-safety applications, but safety-instrumented functions require F_CH_AI or F_CH_DI.
What does output QBAD indicate on F_CH_AI?
QBAD = 1 indicates that the channel is passivated due to a wire break, hardware fault, or discrepancy error.
How is a passivated fail-safe channel reintegrated?
By pulsing the ACK_REI (Acknowledge Reintegration) input pin after the field sensor fault is cleared.
What parameter on F_CH_AI receives the raw hardware address?
The VALUE parameter connects to the process image input symbol (e.g., IW 512).
Where can an engineer review detailed driver generation logs?
In SIMATIC Manager under the compiler log window or the text file CFC_LOG.TXT in the project directory.

Technical References

SIMATIC S7 F/FH Systems - Configuring and Programming Manual
SIMATIC PCS 7 CFC for S7 / PCS 7 Manual
Siemens Industry Online Support Entry: Troubleshooting F-Channel Driver Generation (Entry ID 299714)
SIMATIC Safety - Transitioning from S7 F-Systems to TIA Portal Safety