Troubleshoot CEMAT FB 1002 Accessing an Unloaded Data Block

If a PCS 7 V8.2 AS enters STOP after compiling or downloading a chart that uses CEMAT FB 1002 (C_DAMPER), first use the CPU diagnostic buffer to identify the exact missing data block and determine which block or CFC reference requests it. Siemens' CEMAT V8.2 manual documents how to keep the project library's blocks and the AS block container aligned, but the available documentation does not confirm that copying all CEMAT FBs repairs the particular DB 680, DB 678, or DB 643 reported in this case.

Symptoms and scope

The reported symptom was that the CPU in PLCSIM entered STOP after a CFC compile/download in a PCS 7 V8.2 project using CEMAT blocks, while PCS 7 V8 application-library functions did not show the same problem. The CPU diagnostics were reported to identify an unloaded DB accessed by FB 1002 (C_DAMPER). DB 680, DB 678, and DB 643 were later named as DBs that had not appeared after compilation. These DB numbers and the troubleshooting result are observations from this project, not standard CEMAT DB numbers established by the cited manual.

Why compiling a chart may not create the reported DB

The CPU diagnostic points to an access to a DB that was not available in the loaded program. The important next fact is the exact DB number and the access context shown in the diagnostic buffer. A missing referenced DB could be a required project data block, but the material available does not establish whether the named DB should be generated from a particular CFC instance, provided by project configuration, or included through a CEMAT-specific project component. Do not assume that recompiling FB 1002 alone will create every DB it references.

Method: trace and reconcile the missing block

Preserve the complete CPU diagnostic entry, including the DB number and the block/access information reported with it. Do not infer that loading FB 1002's instance DB covers every DB accessed by that FB.
In the offline AS program, search for the exact missing DB and trace the reference to the calling block or configured CFC object. Record whether the reference is a configured instance, an explicit block parameter/reference, or another project dependency; the ticket does not provide enough detail to prescribe a particular project-specific source.
Compare the AS block container with the project's designated CEMAT project library and the installed CEMAT V8.2 library. Siemens' CEMAT V8.2 Engineering Manual describes the project library as containing the CEMAT symbols, blocks, and charts used in the project, and directs engineers to copy project-library symbols and blocks into the AS program and place the system chart in the AS plant view.
If the project library or AS block set is incomplete, reconcile it using the documented CEMAT V8.2 engineering workflow and the project's established library/version control. The same manual describes updating the CFC chart folder from the offline block folder to make CEMAT block types available in the CFC catalog. That preparation step is not proof that any arbitrary missing DB will be generated.
Recompile the affected CFC/AS program and review the compile diagnostics for unresolved references. Before loading changes to a real controller, apply the site's review, backup, outage, and rollback process. The ticket reports a PLCSIM test environment, not a validated live-plant procedure.

Expected result and recovery evidence

A meaningful recovery requires more than an accepted compile or a downloaded FB. Confirm that the exact DB called out by the CPU diagnostic is present in the intended offline/online program state and that the diagnostic no longer identifies that missing access after the controlled test. The ticket reports that copying the missing data blocks from another project resolved its immediate PLCSIM symptom, but provides no block contents, source project provenance, version comparison, or subsequent diagnostic record. Treat that result as case-specific and do not copy a DB from another project into a production controller without confirming its purpose and compatibility.

What the CEMAT manual establishes

The Siemens CEMAT V8.2 Engineering Manual's installation chapter explains how to create a project library from the installed CEMAT library, including the complete CEM_ALL program folder from ILS_CEM and, for a project-specific standard, blocks from PRO_CEM. It then instructs copying project-library symbols and blocks to an AS and adding the SYSPLC00 system chart in the plant view, with a name adapted to the AS. It also describes copying offline block types into the chart folder for CFC engineering. These are library/project setup requirements; they do not identify DB 680, DB 678, or DB 643 or prove that copying every FB is the correction for this diagnostic.

Verification

Verify the diagnosis against the full CPU diagnostic entry and the actual project configuration, not just the DB number mentioned in a reply. Check that the block library used by the AS and CFC chart folder belongs to the intended CEMAT V8.2 project standard, that required project-library blocks are present, and that the relevant chart compiles without unresolved references. In a controlled PLCSIM test, observe whether the CPU remains in RUN and whether the specific missing-DB diagnostic clears. Do not describe that outcome as a production validation.

Limitations and Operational Precautions

The source omits the diagnostic-buffer text, the identity and contents of the missing DBs, the CEMAT project key/standard, library revisions, and which CFC object or code path requests each DB. Consequently, the root cause and the exact repair cannot be confirmed. The ticket's copied-DB workaround is not independently validated, and its later recommendation to copy all FBs does not by itself explain how the missing DBs are produced. Use the manual's library workflow only when it matches the project's actual CEMAT version and library architecture. Changes to AS blocks, DB contents, compile output, or downloads require the site's normal change control and an appropriate test/rollback plan.

Engineer FAQ

Does FB 1002's instance DB necessarily account for every DB it accesses? No. The diagnostic described in the source identifies an unloaded DB accessed from FB 1002; determine the exact DB and reference rather than assuming the instance DB is the only dependency.

Does Siemens' CEMAT V8.2 manual say to copy all FBs to fix DB 680, DB 678, or DB 643? No. It documents project-library setup and transferring the library's blocks into the AS program, but does not mention those DB numbers or confirm that copying all FBs repairs this case.

Can missing DBs be copied from another project? That workaround reportedly cleared this PLCSIM symptom, but the source does not establish the DB contents or compatibility. Identify the DB's role and confirm it belongs to the same project standard and CEMAT configuration before reuse.

What is the first useful evidence to collect? Capture the full CPU diagnostic-buffer entry identifying the missing DB and access context, then trace that reference in the offline AS/CFC project.

Technical References

Siemens, Engineering Manual CEMAT V8.2, installation of a PCS 7 project, §§3.3–3.4, pp. 3-41–3-47 (project library creation; copying CEMAT symbols, blocks and system chart to the AS; preparing chart-folder block types; compiling CFC): https://cache.industry.siemens.com/dl/files/911/109745911/att_913675/v1/Cem_V82_Engineering_000_en.pdf

Related Tags

CEMAT, PCS 7 V8.2, CFC, CPU diagnostics

Troubleshoot CEMAT FB 1002 Accessing an Unloaded Data Block