101016

Access the PLC program via SIMATIC Manager or HMI Advanced. Note the exact block number and operand type displayed with the alarm (typically shown in diagnostic buffer).

Review all indirect addressing and indexed operations in the suspect PLC block (FC, FB, or OB). Look for operations using pointers, array indices with calculations, or ANY_POINTER operations.

Check loop counters and index calculations for potential overflow conditions. Verify that all index multipliers and offsets cannot exceed 65535 under any operating condition.

Ensure machine is in a safe state before modifying PLC code. Incorrect changes can affect machine safety functions.

Add range checking logic before indexed operations to limit calculated addresses to maximum 65535. Reload the modified PLC program, clear the alarm, and test the affected functionality.

Access the PLC configuration and identify the data block referenced in the alarm message. Open the DB in SIMATIC Manager and check its declared size and structure.

Review all symbolic and absolute addressing within the DB. Check if any DB byte offset (DBX, DBW, DBD addresses) exceeds 65535 or references memory beyond the declared DB length.

If the DB size legitimately needs to exceed 64KB, restructure the data into multiple smaller DBs (max 64KB each) and modify the accessing logic accordingly.

Back up the entire PLC program before restructuring data blocks. Document all changes for maintenance records.

Correct the DB structure or addressing, download the modified configuration to the NCU, perform a memory reset if necessary, and verify all associated read/write operations function correctly.

Identify the active NC program block when the alarm occurred. Check the alarm diagnostic buffer for the exact line number and review the program at that location.

Examine all R-parameter assignments, GUD/LUD variable addressing, and indirect parameter accesses. Look for calculated addresses using formulas that could result in values greater than 65535.

Review synchronized actions and compile cycles that may reference system variables or machine data with excessive address values. Check for typing errors in direct numeric addresses.

Note the original program values before making changes for documentation and potential rollback.

Correct the addressing error in the NC program, ensuring all variable and parameter addresses remain within valid ranges (typically R0-R999, specific limits for GUD/LUD). Reset the program, clear the alarm, and test in single-block mode.