SIEMENS 6ES5945-7UA13
- EICHLER-art.no.: K0117885
- EAN: 4025515056102
Product description
SIMATIC S5, CPU 945 FOR S5-115U 256 KB
Services for SIEMENS 6ES5945-7UA13
SIEMENS |
6ES5945-7UA13 –
additional product information
| Delivery information | |||
|---|---|---|---|
| Export identifier | AL: ECCN: | ||
| Net weight | 0.819 | ||
| Quantity | 1 Stück | ||
| Packaging quantity | 1 | ||
| Additional product information | |||
|---|---|---|---|
| Product status | EOP: 2005-10-01 | ||
| EAN | 4025515056102 | ||
| UPC | / | ||
| Static lot number | 85371091 | ||
| List indicator | / | ||
| Product group | 4235 | ||
| Country of origin | DE | ||
| Compliance with the substance restrictions according to RoHS directive | Since: / | ||
| Product classifications | Version | Classification | |
|---|---|---|---|
| eClass | 4 | / | |
| eClass | 5.1 | / | |
| eClass | 6.0 | / | |
| ETIM | 3 | / | |
| ETIM | 4 | / | |
| ETIM | 5 | / | |
What is 6ES5945-7UA13 and where is it used?
The 6ES5945-7UA13 is a SIMATIC S5 CPU 945 for the S5-115U automation system, featuring 256 KB of memory. As the central processing unit, it executes the control program and is primarily found in existing machines, production lines and special-purpose systems that continue to operate with SIMATIC S5 and STEP 5. For maintenance personnel, the module is particularly important when an existing S5 architecture must remain in service without major modifications. For procurement teams, the exact part number is critical because, with obsolete PLC components, even small variations can affect compatibility, repairability and sourcing risk. In legacy installations, the precise identification of manufacturer, system family and MLFB helps minimise downtime and avoid incorrect orders.
Overview of the key technical specifications and what they mean
Technically, the CPU 945 is a central processing unit for the S5-115U with 256 KB of memory. Siemens also specifies an integrated real-time clock for time and calendar functions. For more demanding legacy applications, the CPU 945 can address DX blocks and offers additional functionality compared with earlier S5-115U CPUs. Siemens documentation further confirms support for floating-point operations. In practice, this makes the module particularly suitable for installations requiring larger memory capacity, more complex data handling or advanced mathematical functions. When replacing or repairing a CPU, it is therefore important to consider not only the physical form factor but also memory requirements, the STEP 5 program structure and the CPU-specific functions used within the application.
Product status, life-cycle status and obsolescence
For the 6ES5945-7UA13, obsolescence is a major consideration. The EICHLER product page lists an EOP (End of Production) date of 2005-10-01. Siemens still references the part number as a spare part in current product information, while the Siemens Industry Online Support and SiePortal information indicate that the product is at the end of its life cycle. Siemens' migration documentation also states that SIMATIC S5 was discontinued in 2003, and that the overall SIMATIC S5 product life cycle officially ended on 30 September 2020. Since 1 October 2020, spare parts and repair services for S5 systems have no longer been available directly from Siemens. No verified direct plug-and-play successor has been identified in the available Siemens documentation. For migration projects, Siemens only provides indicative S7-1500 alternatives such as the CPU 1516-3 PN/DP, CPU 1517-3 PN/DP and CPU 1518-4 PN/DP, explicitly not as automatic 1:1 replacements.
Available EICHLER services and when they are relevant
For the 6ES5945-7UA13, EICHLER offers repair, exchange, used units and new units. Repair is particularly attractive when the existing S5-115U configuration should remain unchanged and the installed CPU can be economically restored. According to the product page, repair services are available with a 2–5 day turnaround time, an optional test report, and include technical cleaning, preventive maintenance, comprehensive functional testing and a minimum 24-month warranty. Exchange services are ideal when downtime costs outweigh any additional testing or shipping time. Used and new units support the creation of strategic spare-part inventories for S5-based systems. EICHLER also highlights life-cycle management services such as inventory analysis, spare-part management and supply strategies, helping operators maintain system availability even after manufacturer support has ended.
| Fault description | Possible solution |
|---|---|
| Why does my S5-115U with CPU 945 behave differently after a cold start or lose retentive data? | First check the position of the NR/RE startup selector switch and the configured startup mode. Siemens states that for CPU 941 to CPU 945, a cold start with the switch set to NR resets markers, CPU 945 S-markers, timers and counters. If the behaviour after power restoration is unexpected, review the startup concept, retentive data strategy and the storage method used for variable data blocks. It should also be verified whether important DB contents are stored only in volatile RAM and therefore are not retained after power-on. |
| How can I access data words above address 255 on the CPU 945? | Siemens describes a special procedure for the CPU 945, because only 16 bits per block entry are available in the address list. If data words above DW 255 must be read or written, standard addressing methods are not sufficient. In such cases, memory access must be implemented according to the programming method specified by Siemens. If high-address data words return incorrect values or cannot be accessed, these addressing routines should be checked first and adapted where necessary. |
| Why does FB IM308C report error 00B0H or QVZ on the CPU 945 during the first job? | Siemens identifies this as a specific characteristic of the CPU 945. When FB IM308C is used, the first job is not executed; the error code 00B0H (QVZ) stored in DW 8 should be ignored in this particular situation. For troubleshooting, do not evaluate the first diagnostic entry in isolation. Instead, observe the subsequent cycle and the continuing communication with the IM 308-C. If communication operates normally afterwards, the issue is most likely this known CPU 945 behaviour rather than a permanent communication fault. |
| Why does a program block containing the MBA instruction not work correctly on the CPU 945? | Siemens documentation for the CPU 945 notes a restriction: the DBS register may only be set using Operating System Service 21 in OB 250. Siemens recommends replacing problematic MBA usage with the instruction sequence ABR+0, MBA. If a program behaves unexpectedly after a CPU replacement, firmware change or software modification, this section of the STEP 5 code should be examined carefully. |
| Why are modified data blocks restored to their previous values after Power ON? | In S5-115U systems, data blocks may be reloaded from EPROM into RAM during startup. Practical experience with the S5-115U family shows that modifications to data blocks can be lost after a power cycle if the relevant DBs are configured as EPROM-based rather than RAM-based. If setpoints, counters or recipe data revert to old values after power restoration, the storage strategy for the affected data blocks and the long-term retention method for critical process values should be reviewed. |
Is 6ES5945-7UA13 still available or only on the aftermarket?
From today's perspective, the 6ES5945-7UA13 is clearly a product intended for maintaining existing installations. Siemens still lists the part number as a spare part, while the Siemens Industry Online Support portal indicates that the product has reached the end of its lifecycle. Siemens also specifies 30 September 2020 as the end of the SIMATIC S5 product lifecycle. In practice, this means that availability is typically no longer based on regular manufacturer supply, but rather on repair, exchange services, refurbished units and, in some cases, remaining new-old-stock inventory. This is exactly why service providers with testing and repair expertise are particularly important for this article number.
Is there a direct successor to 6ES5945-7UA13?
No direct, plug-compatible successor officially designated by Siemens could be identified in the available Siemens documentation. Instead, Siemens refers users to migration paths from SIMATIC S5 to the SIMATIC S7-1500 platform and lists CPUs such as the CPU 1516-3 PN/DP, CPU 1517-3 PN/DP and CPU 1518-4 PN/DP as possible target systems. At the same time, Siemens emphasises that these comparisons are intended only as guidance and do not imply automatic functional equivalence. Anyone looking for a true 1:1 replacement should therefore not assume a direct hardware substitution, but rather evaluate the options of repair, replacement within the S5 environment or a planned migration project.
When is repair more appropriate than replacement?
Repair is generally the better option when the existing module remains mechanically and functionally repairable and the current S5-115U environment is intended to remain unchanged. This is often the preferred approach when existing wiring, software, commissioning status and documentation should be preserved. Replacement, on the other hand, becomes more attractive when downtime costs are extremely high and immediate availability is more important than receiving the original CPU back. According to the EICHLER product information, repairs are typically completed within 2–5 days, while exchange, refurbished and new units are also available for this part number.
Can I replace a 6ES5945-7UA13 directly with an S7-1500 CPU?
An S7-1500 should not be considered a direct replacement. Siemens clearly states in its migration guides that the comparison tables are intended only for orientation and that the technical characteristics of the existing and new hardware must be evaluated in detail. This includes aspects such as power supply requirements, signal types, communication interfaces, channel concepts and the actual customer application. In practice, this means that migration is possible and often advisable in the long term, but it should be treated as an engineering project rather than a simple CPU swap.
How do I know when I need an obsolescence strategy rather than individual spare-part purchases?
Once an installation contains several S5 modules, limited spare-part availability, uncertain stock levels or recurring procurement issues, purchasing individual spare parts is often no longer sufficient. Siemens notes that the number of available S5 spare parts continues to decline. For this reason, EICHLER positions its Life Cycle Management services around inventory assessment, structured asset data, stock management and long-term supply strategies. This becomes particularly important when not only a single CPU but entire sections of a plant are affected by the same obsolescence risks.
Which procurement strategy is best for a CPU 945: refurbished, exchange or new?
The best approach depends largely on the intended application. An exchange unit is usually the preferred option when production downtime must be minimised immediately. A refurbished unit is often suitable when building a cost-effective spare-parts inventory for existing installations. A new unit is most appropriate when an unused device is required for strategic spare-part stockholding or to satisfy specific quality requirements. EICHLER offers all four options for the 6ES5945-7UA13 – repair, exchange, refurbished and new – and explicitly describes new units as a means of establishing reliable spare-part inventories. For obsolete S5 systems, the key consideration is therefore not only price, but also how availability, risk and downtime are weighted.
