A modern automation cabinet is basically a controlled argument between physics and scheduling. Sensors generate messy signals, networks have jitter, actuators demand timing, and safety requirements insist that “mostly correct” is not a thing. The Siemens 6ES7517-3FP00-0AB0 sits right at that intersection: it is a SIMATIC S7-1500F fail-safe CPU, type CPU 1517F-3 PN/DP, engineered for fast deterministic control, multi-network connectivity, and integrated safety functionality.
This CPU combines large controller resources with industrial communications in a single central unit: 3 MB work memory for program, 8 MB work memory for data, and a plug-in SIMATIC Memory Card (required) providing load memory up to 32 GB. Its communications layout targets real plant architecture: PROFINET IRT with an integrated 2-port switch, a second PROFINET RT interface, and a built-in PROFIBUS DP interface.
What makes the 1517F class interesting isn’t just “it’s fast.” It’s fast in the ways that matter for automation: Siemens specifies typical execution times of 2 ns for bit operations, 3 ns for word operations, 3 ns for fixed-point arithmetic, and 12 ns for floating-point arithmetic. That kind of performance helps when you need to keep cycle times stable while also handling diagnostics, communication load, technology objects, and (crucially) safety logic.
Built for real networks, not brochure networks
The CPU’s interfaces are designed for mixed topologies and staged migrations:
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Interface X1: PROFINET IRT via RJ45 with 2 ports and an integrated switch (good for line or ring wiring without an external switch).
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Interface X2: PROFINET RT via RJ45 with 1 port (often used for a second network segment or separation of traffic).
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Interface X3: PROFIBUS via RS-485, with PROFIBUS DP master capability.
For plant-wide scale, Siemens specifies up to 320 connections total (via integrated interfaces and connected CPs/CMs), with 288 connections via integrated interfaces, and reserves 10 connections for ES/HMI/web. On the PROFINET IO controller side, Siemens lists up to 512 connectable IO Devices, and notes up to 64 IO devices with IRT. For PROFIBUS, the integrated DP interface supports up to 125 DP slaves (and up to 48 connections for the integrated PROFIBUS DP interface).
Integrated safety where it counts
This is an S7-1500F CPU, meaning it is designed for fail-safe applications. Siemens states the highest safety class achievable in safety mode as PLe (ISO 13849-1) and SIL 3 (IEC 61508). It also provides probability-of-failure metrics for a 20-year service life assumption: PFDavg < 2.00E-05 for low-demand mode and PFH < 1.00E-09 for high-demand/continuous mode (both aligned with SIL3 context).
For safety networking, the datasheet lists PROFIsafe support (V2.4 / V2.6). In practice, that helps when you’re building safety functions across PROFINET/PROFIBUS landscapes while keeping engineering consistent in the SIMATIC ecosystem.
Motion control and process control features in one CPU
If your machine is part PLC and part motion system, CPU resources can vanish fast. Siemens specifies Motion Control support and quantifies resources: 10,240 Motion Control resources are available, with typical resource costs per technology object (for example 80 per positioning axis, 160 per synchronous axis). Siemens also provides typical axis counts: 70 positioning axes at a 4 ms motion control cycle and 128 positioning axes at an 8 ms cycle (typical values).
On the control side, the CPU supports Siemens controller blocks such as PID_Compact, PID_3Step, and PID-Temp, and includes high-speed counting capability. That matters when a single controller must handle discrete logic, basic process loops, and coordinated motion without turning your cycle time into a horror story.
Key Technical Specifications (condensed)
| Category | Specification |
|---|---|
| Product / CPU type | SIMATIC S7-1500F, CPU 1517F-3 PN/DP (6ES7517-3FP00-0AB0) |
| Work memory | 3 MB program, 8 MB data |
| Load memory | SIMATIC Memory Card required; up to 32 GB |
| Performance | Bit operations 2 ns typ.; word 3 ns typ.; floating point 12 ns typ. |
| Interfaces | PROFINET IRT X1 (2-port switch), PROFINET RT X2, PROFIBUS DP X3 (RS-485) |
| PROFIBUS DP | DP master yes; RS-485 up to 12 Mbit/s; up to 125 DP slaves |
| PROFINET IO | Up to 512 IO devices, up to 64 IRT devices |
| Connections | Max 320 total connections; 288 via integrated interfaces |
| Security / web | Web server HTTP/HTTPS; encryption optional for Open IE communication |
| OPC UA | OPC UA client/server; runtime license required; security policies listed |
| Safety | Up to PLe and SIL 3 in safety mode; PFDavg/PFH values provided |
| Power | 24 V DC (19.2–28.8 V); current consumption 1.55 A; power loss 24 W typ. |
| HMI / local operation | Display 6.1 cm, 6 keys, mode selector switch |
| Environmental | Operation: 0–60 °C horizontal (display off typically at 50 °C); 0–40 °C vertical (display off typically at 40 °C) |
| Dimensions / weight | 175 × 150 × 129 mm, 2100g |
Where this CPU is a strong fit
| Application | Why 6ES7517-3FP00-0AB0 makes sense | Practical note |
|---|---|---|
| High-performance machines with safety | SIL3/PLe capable safety mode, strong CPU performance, PROFIsafe support | Safety performance depends on complete system design and validation |
| Mixed PROFINET + PROFIBUS plants | Integrated PROFINET + PROFIBUS DP master in one CPU | Useful for phased modernization without ripping out fieldbus immediately |
| Motion-heavy packaging/assembly lines | Quantified Motion Control resources and axis capacity guidance | Axis count impacts PLC cycle time, so size the application realistically |
| Data-driven automation | OPC UA client/server with defined security policies (license required) | Plan licensing early if OPC UA is a project requirement |
| Commissioning and diagnostics focus | Diagnostic buffer, traces (up to 8), and standard CPU indicators | Trace use is a practical way to shorten commissioning time |
Summary
The Siemens 6ES7517-3FP00-0AB0 (CPU 1517F-3 PN/DP) is a high-end SIMATIC S7-1500F fail-safe CPU built for deterministic control, mixed-network plants, and safety-oriented machine design. With 3 MB program and 8 MB data work memory, load memory up to 32 GB via SIMATIC Memory Card (required), and execution times down to 2 ns typical for bit operations, it is designed for applications where cycle time, communication load, and safety logic all coexist. It integrates PROFINET IRT (2-port switch), a second PROFINET RT interface, and PROFIBUS DP master, and supports capabilities like OPC UA (runtime license required), HTTPS web server, optional encryption, and Motion Control features with quantified resources and axis guidance.
