Which STEP 7 Manuals Explain Local Data, Cycle Time and Operator Variables?

For a PCS 7 V9.0 SP1 project, use Siemens' PCS 7 Engineering System (V9.0 SP1) Configuration Manual for PCS 7 hardware planning, and Programming with STEP 7 for program structure, symbolic names, local data and operator-control/monitoring variables. The latter manual explains that temporary local data are held in a CPU local-data stack while a block is active, and that available sizes depend on the CPU. “ES variables” is not precise enough to identify a single memory area, so confirm whether the question concerns WinCC operator variables, STEP 7 symbols, or CPU storage.

Manuals to start with

For the version named in the original discussion, Siemens' PCS 7 Engineering System (V9.0 SP1) Configuration Manual (12/2017, A5E39219444-AC) covers PCS 7 engineering and CPU hardware selection. Its §4.8.4 lists default CPU performance and memory-related parameters for the CPU models covered; those tables are version- and CPU-specific.

For STEP 7 program concepts, Siemens' Programming with STEP 7 manual (04/2017, A5E41552389-AA) is a separate reference. The relevant subjects include §4, program structure and scan-cycle considerations; §8, symbols; §17, variables for operator control and monitoring; and §26.2, S7 CPU memory areas and local-data stack.

Understand local data versus other memory

In the cited STEP 7 manual, local data are temporary block data stored in the CPU's local-data stack. They are available while the block is active; the stack also carries OB start information and block-parameter transfer data. This is distinct from shared symbols, bit memory, process-image I/O and data blocks. Do not assume that a temporary local variable retains its previous value after the block call ends.

The amount of local-data memory is CPU-dependent and divided among priority classes. The manual explains that S7-400 and CPU 318 allocations can be configured by priority class, while other S7-300 CPUs have fixed allocations in the described system. Use the manual and instruction list for the exact CPU model rather than applying one example's capacity universally.

Understand cycle time in context

Cycle time is not a single fixed value applicable to every PCS 7 controller. It depends on CPU configuration, user-program execution, communication load and asynchronous events such as cyclic or hardware interrupts. STEP 7's manual explains that configured communication load can extend OB1 scan time and that interrupts also affect the actual scan cycle. PCS 7 V9.0 SP1 CPU tables list default cycle-monitoring and minimum-cycle parameters, but these are not a substitute for the target CPU's performance documentation or measured project behavior.

Distinguish symbols from operator variables

STEP 7 symbols provide readable names for addresses; they are not themselves a separate memory allocation. The STEP 7 manual's §8 discusses symbolic addressing and shared/local symbols. Its §17 describes configuring variables for operator control and monitoring and transferring generated configuration data to WinCC using AS-OS Engineering. Those WinCC-facing variables and their configuration should not be confused with the CPU's TEMP/local-data memory.

If “ES variables” means variables configured at the Engineering Station, clarify whether the question is about operator-control/monitoring attributes, online test/monitor variables, or memory consumed by CPU program variables. These are different topics.

How to use the references

Identify the PCS 7 release and exact CPU model from the project and hardware configuration.
Read the PCS 7 Engineering System manual's hardware-selection section for version-specific PCS 7 defaults and planning context.
Read Programming with STEP 7 §4 for program execution and scan-cycle concepts, §8 for symbols, §17 for operator-control/monitoring variables, and §26.2 for CPU memory areas and local data.
Confirm model-specific memory capacities and limits in the applicable CPU manual or instruction list cited by Siemens.
For the actual project, inspect the configured CPU properties and relevant block declarations; do not infer runtime memory use solely from a generic manual table.

Verification

Confirm the manual edition matches the project release, then confirm the exact CPU model. For local-data questions, inspect the CPU-specific local-data allocation and block temporary-variable requirements. For cycle-time questions, distinguish the configured minimum-cycle and monitoring settings from actual measured OB1 execution and interrupt load. For operator variables, trace the STEP 7/PCS 7 configuration through AS-OS Engineering to the WinCC variable configuration.

Limitations and Operational Precautions

The reply identifies PCS 7 V9.0 SP1 but does not state a CPU model or define “ES variables memory.” CPU capacities and configuration limits vary by model and software generation; the STEP 7 programming manual is dated 2017 and applies to the documented STEP 7 context. Check the current project's version-specific documentation and hardware configuration before using numeric limits. Avoid changing CPU memory, cycle monitoring, or communication-load settings in a running process without engineering review and site change control.

Engineer FAQ

What does local data mean in STEP 7? It refers to temporary block data held in the CPU local-data stack while a block is active, along with other call-related information.

Are STEP 7 symbols stored in CPU memory? A symbol is a symbolic name for an address or variable; the symbol table itself is an engineering representation and does not by itself allocate runtime memory.

Which manual covers PCS 7 V9.0 SP1 hardware? Siemens' PCS 7 Engineering System (V9.0 SP1) Configuration Manual, particularly §4.8 for AS component selection and CPU parameters.

Where are operator variables documented? The 2017 Programming with STEP 7 manual §17 describes operator control and monitoring variables and transfer of configuration data to WinCC.

Can one CPU table be used for all PCS 7 projects? No. Hardware defaults and available memory depend on CPU model and release; use the matching product documentation.

Technical References

Siemens, Engineering System (V9.0 SP1), Configuration Manual, 12/2017, A5E39219444-AC, §4.8.4, CPU performance defaults and related parameters: https://cache.industry.siemens.com/dl/files/984/109754984/att_939418/v1/ps7phesb_en-US.pdf
Siemens, Programming with STEP 7, Manual, 04/2017, A5E41552389-AA, §§4, 8, 17 and 26.2: https://cache.industry.siemens.com/dl/files/825/109751825/att_933142/v1/STEP_7_-_Programming_with_STEP_7.pdf

Which STEP 7 Manuals Explain Local Data, Cycle Time and Operator Variables?