CPU 1513-1 PN vs 1512SP-1 PN: Siemens S7-1500 CPU Selection Guide

Overview: Centralized vs Distributed S7-1500 CPU Selection

Specifying an S7-1500 control system always begins with a topology decision: do you want a central-rack CPU in an S7-1500 mounting rail with conventional SM 5xx I/O, or do you want a distributed controller that lives inside an ET 200SP station next to its I/O modules? Two controllers define that fork in the road: the CPU 1513-1 PN (6ES7513-1AL02-0AB0), a central-rack S7-1500 part, and the CPU 1512SP-1 PN (6ES7512-1DK01-0AB0), an ET 200SP CPU that snaps into a BaseUnit and exposes its PROFINET through a separate BusAdapter (BA). Both run the same TIA Portal project and the same S7-1500 firmware family, so from a programming perspective they are interchangeable. From a hardware, footprint, and field-service perspective they are very different.

For a retrofit project that is replacing the CPU while keeping the existing I/O in place, the choice collapses to a simple question: are the existing I/O modules SM 5xx in a central rack, or ET 200SP modules distributed on a standard 35 mm DIN rail? That one question resolves the rest of the comparison. For new machines, the same question applies: do you want a single control cabinet where all I/O homeruns, or do you want a distributed architecture where each skid carries its own CPU and I/O island?

This reference compares both controllers across memory, execution speed, PROFINET port count, mechanical footprint, display, I/O capacity, motion/PID resources, firmware, security, and field-service behavior, and ends with a selection matrix, commissioning notes, diagnostic buffer interpretation, and a FAQ covering the most common engineering questions.

Catalog Identification, MLFB Encoding, and Hardware Variants

Siemens identifies each S7-1500 CPU by an MLFB (Machine-Readable Product Designation) number that encodes the firmware generation and the hardware feature set. The two current production parts are:

• 6ES7513-1AL02-0AB0 — CPU 1513-1 PN, firmware V2.9, integrated display, two PROFINET interfaces (X1 with 2-port switch, X2 single port), S7-1500 form factor (35 mm wide).
• 6ES7512-1DK01-0AB0 — CPU 1512SP-1 PN, firmware V2.9, no display, integrated 3-port PROFINET switch exposed through a separate BusAdapter, ET 200SP form factor (80 mm wide).

The trailing AB0/AB code indicates the product version. Earlier V1.x and V2.0/2.5/2.6/2.8 generations carry different suffix digits; project migration in TIA Portal is one-way upward and may require a hardware upgrade of the CPU if the older firmware is no longer available. For new projects in 2024 and 2025, target V2.9 as the baseline. Newer firmware V3.x variants may have rolled out for the same MLFBs; always verify on the Siemens Industry Online Support portal before ordering. The 1512SP-1 PN also has a fail-safe sibling, 6ES7512-1SK01-0AB0 (CPU 1512SP F-1 PN), which carries the same PROFINET architecture and adds SIL 3 / Cat. 4 / PL e safety functions. This comparison focuses on the standard variant; the F-variant is selected only when the project has a safety-integrated PROFINET IO chain (e.g. ET 200SP F-modules, SINAMICS with integrated safety).

The 1512SP-1 PN requires a BusAdapter (BA) ordered separately. The most common choices are:

For 95% of installations, the BA 2xRJ45 (6ES7193-6AR00-0AA0) is correct. Fiber variants are used when the IO island is more than 100 m from the CPU, or when galvanic isolation between cabinets is required (different ground potentials, or noisy VFD cabinets).

Performance, Memory, and Execution Time Comparison

The 1513-1 PN is the higher-performance controller. The execution times and work-memory figures below are the deciding factors for programs that push the cycle-time boundary or that are heavy on SCL math and GRAPH sequencers.

For typical PLC programs with cycle times in the 1 - 10 ms range, both CPUs are over-provisioned. The 1513-1 PN's 60% faster bit-operation time and 50% faster floating-point time become relevant in three scenarios:

1. Heavy GRAPH sequencer applications with 20+ steps, each with interlocks and supervision.
2. SCL math-heavy code: complex filter calculations, recipe scaling, or model-predictive blocks.
3. Large recipe / data block structures in retentive memory. A 1513-1 PN keeps 700 KB of data after power-off; a 1512SP keeps 350 KB.

If the project fits comfortably in 200 KB of active code and 350 KB of retain data, the 1512SP-1 PN is the better value.

PROFINET Interface Architecture and Network Topology

The two controllers expose PROFINET very differently, and the topology implications matter more than the raw port count.

CPU 1513-1 PN: Two independent PROFINET interfaces built into the module.

• X1: 2-port managed switch (RJ45), used as the PROFINET IO line.
• X2: 1 additional port, configured as a separate PROFINET subnet (different IP range, separate IO controller role).

CPU 1512SP-1 PN: One PROFINET interface, exposed as a 3-port switch through a single BusAdapter. All three ports share one IP address and one PROFINET device name; they are switched ports on the same subnet.

Topology implications:

• If you need more than 2 PROFINET drops on the same subnet without an external switch, the 1512SP-1 PN has the advantage. The 3-port switch is integrated; daisy-chain the IO islands and still have a port for the SCADA HMI or an engineering laptop.
• If you need physical separation between the IO network and the HMI / management network, the 1513-1 PN's X2 port is the cleaner answer. The X2 port can be on a different subnet, with its own IP range, and a firewall / NAT between the two.
• Both CPUs support PROFINET IO Controller and IO Device roles, and both can act as an I-Device for controller-to-controller data exchange. Both support PROFINET IRT (Isochronous Real-Time) with V2.5+ firmware; on the 1512SP, IRT is supported across the 3-port switch with the appropriate BA.
• Both support MRP (Media Redundancy Protocol) for ring topologies, with the same role: MRP client. To close an MRP ring with a 1512SP, use P1 and P2 as the ring ports and P3 for non-ring devices (HMI, laptop). To close an MRP ring with a 1513, use the two ports of X1 as the ring ports and X2 for the HMI/management network.

Mechanical Form Factor, Mounting, and BusAdapter Options

CPU 1513-1 PN uses the S7-1500 form factor, 35 mm wide, and mounts on a SIMATIC S7-1500 mounting rail (a profiled aluminum rail with integrated backplane). The rail is not optional. Common rail MLFBs:

• 6ES7590-1AB60-0AA0 — 482 mm rail
• 6ES7590-1AC40-0AA0 — 530 mm rail
• 6ES7590-1AD00-0AA0 — 830 mm rail
• 6ES7590-1AE80-0AA0 — 2000 mm rail (cut to length)

The full station consists of a System Power Supply (PS 25W 6ES7505-0AB00-0AB0, or PS 60W 6ES7505-0HA00-0AB0), the CPU, and up to 30 SM 5xx signal modules in the central rack (plus another 30 in an extension rack, for 60 modules total per 1513 station). The station dimensions: 147 mm tall, 129 mm deep for the CPU; the SM 5xx modules are 35 mm wide and snap into the rail's backplane.

CPU 1512SP-1 PN uses the ET 200SP form factor, 80 mm wide, and plugs into a Type C0 or Type C1 BaseUnit. Common BaseUnit MLFBs for the CPU position:

• 6ES7193-6BP00-0BA0 — Type C0, screw terminals, white
• 6ES7193-6BP00-0BD0 — Type C1, spring terminals, white
• 6ES7193-6BP00-0DA0 — Type C0, screw terminals, gray (for potential group continuity)

The BaseUnit then clips onto a standard 35 mm DIN rail (no proprietary rail). The CPU itself is 117 mm tall and 75 mm deep. Up to 32 ET 200SP I/O modules can be added to the right of the CPU, providing a station width of 32 x 15 mm = 480 mm plus the 80 mm CPU width, for 560 mm of horizontal space.

For cabinets with high vibration (mobile equipment, marine, on-machine mounting), the ET 200SP form factor has an advantage: the spring-terminal BaseUnits and screw-down RJ45 BusAdapter (6ES7193-6AR00-0AA0 has retention screws on the RJ45 jacks) survive cabinet door slams and forklift traffic in the aisle better than the S7-1500 rail's clip-on module latches.

Display, Diagnostics, and Operator Interface

The 1513-1 PN ships with a 3.4 cm (1.3") monochrome display and four mechanical / soft keys. The display is one of the most useful features of the S7-1500 family in field service. It shows:

• CPU operating state (RUN, STOP, STARTUP, ERROR)
• IP address and PROFINET device name
• Diagnostic buffer (last 100 events, scrolled with arrow keys)
• Active alarms and messages from the program
• Force table and watch table (read-only by default)
• RUN / STOP / MRES buttons for mode change and memory reset

The 1512SP-1 PN has no display. The same information is available only through:

• TIA Portal's online view (requires an engineering laptop with TIA Portal installed and licensed)
• The integrated web server (HTTPS, V2.0+; default URL is https://<CPU-IP>/)
• An external HMI panel or SCADA station (WinCC Unified, WinCC Comfort/Advanced)

Whether the missing display is an advantage or a disadvantage depends on the site:

• Advantage: An operator cannot put the controller into STOP or reset it by pressing buttons, eliminating an entire class of human-error stops. Useful in unmanned pump stations and OEM machines deployed in customer plants where unauthorized STOP presses have caused service calls.
• Disadvantage: Troubleshooting a 1512SP in the field without a laptop is harder. In plants with strict laptop policies or where the maintenance staff are not authorized to connect a laptop to the network, the 1513's display is a real serviceability feature.

For OEM machines that ship with their own TIA Portal project on a USB stick and a service contract that includes remote engineering, the missing display is a non-issue. For brownfield plants where the maintenance technicians are the first line of defense, the 1513's display is the safer choice.

I/O Architecture and Distributed Capacity

The 1513-1 PN's local I/O is the SM 5xx family: digital input (SM 521), digital output (SM 522), analog input (SM 531), analog output (SM 532), technology modules (TM Count, TM PosInput, TM Timer, etc.), and communication modules (CM PtP, CM 1542-5 for PROFIBUS). Up to 30 modules can be placed to the right of the CPU in the central rack. With an IM 155-5 PN ST interface module in the rail, the 1513 can also be expanded via PROFINET to additional ET 200MP racks (SM 5xx in distributed racks) for up to 60 SM modules total.

The 1512SP-1 PN's local I/O is the ET 200SP family: digital input (DI 8x24VDC HF, DI 16x24VDC SRC), digital output (DQ 8x24VDC/0.5A HF, RQ 4x120VDC-230VAC/5A), analog input (AI 4xU/I/RTD/TC, AI 8xU/I/RTD), analog output (AQ 4xU/I), technology modules (TM Count 1x24V, TM PosInput 1x24V), and serial modules (CM PtP, CM 4xIO-Link). Up to 32 ET 200SP modules can be placed to the right of the CPU, providing 32 x 8-channel = 256 digital channels in a 480 mm horizontal run.

For both CPUs, the maximum number of IO devices on PROFINET depends on the firmware and project size, not on the CPU alone. As a rule of thumb, the 1513 handles 100+ IO devices comfortably, the 1512SP handles 64 IO devices. Both can act as an IO controller for the local rack and as a PROFINET IO device to a higher-level line controller (the I-Device role).

In the retrofit case where existing I/O is left in place, neither CPU talks to that I/O directly. Both PROFINET interfaces are used to attach to the existing PROFINET network that already carries the existing I/O. The choice between the two CPUs is then purely about the controller's location, form factor, and field-service behavior.

Programming Resources: OPC UA, Trace, Web Server, Motion

Both CPUs support the same TIA Portal project model and the same instruction set. The functional limit differences are below; figures are for V2.9 firmware and may differ on other firmware versions.

OPC UA on both CPUs is configured under Properties > OPC UA Server. The server provides read/write access to a configurable set of DB tags, supports subscriptions at 100 ms minimum publish interval, and uses X.509 certificates for authentication. The web server is enabled under Properties > Web server, with user management (read-only and read/write users) and an optional self-signed certificate for HTTPS. Both services can be disabled per project requirement for cyber-security reasons.

Firmware, SIMATIC Memory Card, and Migration Path

Firmware on S7-1500 is supplied pre-installed and is updated via the SIMATIC Memory Card. Both CPUs use the same card form factor (SD card, formatted with the SIMATIC file system, 4 MB to 32 GB). When migrating an existing S7-1500 project to either of these CPUs, the project must be recompiled in TIA Portal against the new CPU's firmware. Cross-MLFB migration (1512SP ↔ 1513) is straightforward because the firmware family is shared.

Migration caveats:

1. The 1512SP is missing the front display, so the "Display" object cannot be created in the project. TIA Portal will flag this as a warning during compilation; remove the display object or disable it before download.
2. The 1512SP's PROFINET port assignment is the BusAdapter. The BA is configured in TIA Portal under Properties > PROFINET interface > Port assignment. The three ports are labeled P1, P2, P3 by default. PROFINET device names and IP addresses are assigned to the interface, not to individual ports.
3. The 1512SP requires a BaseUnit (Type C0 or C1) and a BusAdapter to function. The CPU is plugged into the BaseUnit, the BaseUnit carries the backplane power to the right-hand I/O modules, and the BusAdapter provides the PROFINET physical layer. Forgetting any one of these results in a CPU diagnostic fault: "BaseUnit type invalid", "BusAdapter not connected", or "PROFINET interface failed".
4. Retentive variables on the 1512SP are limited to 350 KB. A project with 500 KB of retain data (recipe data, historical counters) will fail the compile with a "Retentive memory exceeded" error. Either reduce the retain budget or move to the 1513-1 PN (700 KB retain).
5. Cross-CPU migration (1513 to 1512SP) of a running program requires a stop, an export, a hardware change in TIA Portal, a recompile, and a download. The process is reversible (1512SP to 1513) using the same steps. Always export the original project as a TIA Portal project archive (.zap15) before the migration.

For firmware upgrades, never downgrade firmware on a working CPU. Siemens publishes downgrade blockers in the firmware release notes; the V2.9 firmware cannot be downgraded to V2.5 because of security patches. Treat the firmware as monotonic and verify the new firmware in a lab before applying to production.

Selection Matrix and Application Recommendations

For a typical brownfield retrofit intended to keep the I/O but replace the brain, the 1512SP-1 PN is the better value: it eliminates the cost of the S7-1500 mounting rail and the System Power Supply (the SP takes its power through the BaseUnit), and it gives you a 3-port switch that lets you drop the engineering laptop directly onto the PROFINET line without an external switch.

For a new project with significant program size, custom function blocks, recipe management, and centralized diagnostics, the 1513-1 PN's extra work memory and execution speed are worth the price differential. The display alone can save an entire service visit during commissioning because most diagnostic questions can be answered on the front panel without a laptop.

Commissioning Notes and Field-Proven Cautions

1. TIA Portal hardware catalog. The 1512SP-1 PN is found under "PLC > SIMATIC ET 200 CPU" and the 1513-1 PN is under "PLC > SIMATIC S7-1500". Selecting the wrong catalog path produces an "Incompatible device" compile error and a blocked download.
2. SIMATIC Memory Card format. The card must be the SIMATIC format, not the SD standard. A generic SDHC card from a consumer store will not be recognized; the CPU will report "SIMATIC Memory Card: invalid format". Order 6ES7954-8LPxx-0AA0 (4 MB through 32 GB variants) directly from Siemens. Verify the card write-protect switch is in the unlocked position before insertion.
3. BusAdapter replacement under power. The BusAdapter on a 1512SP can be hot-swapped only on a powered-down module. Removing the BA from a live CPU causes a station failure and a "PROFINET IO failure" diagnostic on the controller, which can stop the line if the CPU is the IO controller for safety-critical I/O. Plan the maintenance window accordingly.
4. PROFINET device name. Both CPUs support the PROFINET DCP (Discovery and Configuration Protocol) for device-name assignment. Use the "Assign PROFINET device name" function in TIA Portal (Online > Accessible devices > PROFINET device) rather than hard-coding IPs. The device name is the only thing that survives a CPU factory reset; the IP is then assigned by the IO controller on startup via the LLDP neighbor relationship.
5. Retentive data budget. The 1513 has 1.5 MB total data work memory, of which up to 700 KB is retentive. The 1512SP has 1 MB total, of which up to 350 KB is retentive. If your project stores large recipes or process history in retain variables, check the retentive budget on the SP variant by opening Properties > PLC > Retentive memory.
6. Spare parts philosophy. If the plant standardizes on a specific CPU, choose the 1512SP-1 PN for distributed skids and the 1513-1 PN for the central line control. This way only two CPU SKUs are in the spares inventory. Mixing 1511SP, 1512SP, 1515, and 1516 on the same line is normal but adds to the spare-parts matrix.
7. Display as a service tool. Always update the diagnostic buffer (Online > Online & Diagnostics > Diagnostic buffer) before reading it on the display. The display's local buffer is a snapshot from the last refresh and can lag the online buffer by 5-10 s on a heavily-loaded CPU. For real-time diagnostics, the TIA Portal view is the source of truth.
8. Firmware update via SIMATIC Memory Card. Copy the firmware .upd file to the root of an empty SIMATIC Memory Card, insert the card into the powered-off CPU, and turn on the CPU. The CPU will flash the firmware automatically. Do not interrupt the power during the update. After the update, remove the card, reformat it, and reload the project.
9. Power-on reset behavior. Both CPUs support the configurable power-on behavior: stay in STOP, go to RUN, or RUN with a warm restart that reinitializes non-retentive data. Configure this under Properties > Startup. For brownfield retrofits, "RUN with warm restart" is usually the right choice because the existing process state is preserved in the I/O.
10. Security settings. Both CPUs support the security level configuration under Properties > Security. V2.9 firmware enables certificate-based authentication for OPC UA, web server, and PG/PC connections by default. Disable any of these if the project does not require them, and configure the user list (read-only and read/write users) to enforce the principle of least privilege.

Diagnostic Buffer Interpretation and Common Faults

When a fault occurs, the diagnostic buffer is the first place to look. Below is a short reference for the most common events on both CPUs.

To export the diagnostic buffer for a support ticket, right-click the CPU in the project tree, choose "Online & Diagnostics > Diagnostic buffer", click "Save As", and export the .dbf file. The exported file can be opened in Microsoft Excel or sent to Siemens Industry Online Support for analysis.

Security, Access Control, and TLS Configuration

Both CPUs support the SIMATIC Security Controller functionality introduced in firmware V2.6 and expanded in V2.9. The relevant features:

• User management. Read-only users, read/write users, and administrator users with separate passwords. The user list is stored on the SIMATIC Memory Card and travels with the project.
• TLS for OPC UA and web server. Both services support TLS 1.2 and TLS 1.3 with X.509 certificates signed by an internal CA or a public CA. Self-signed certificates are generated by TIA Portal at project compile time and can be replaced with CA-signed certificates for production.
• PG/PC connection protection. The PG/PC connection from TIA Portal to the CPU can be configured to require a password. With this enabled, an unauthorized engineer cannot connect to the CPU even if they have the project file.
• Integrity protection. The CPU can be configured to refuse any program modification that has not been signed by the configured TIA Portal project. This prevents an attacker with a laptop from downloading a modified program to the CPU.
• S7 communication protection. PUT/GET, BSEND/BRCV, and other S7 communication functions can be configured to require a password. With this enabled, only authorized CPUs can communicate over S7 connections.

For a 1512SP in a security-sensitive deployment (public-facing network, IIoT gateway), enable all of the above. For a 1513 in a closed plant network with no external connectivity, the integrity protection and the TLS for OPC UA are usually sufficient; the user management and the PG/PC password are nice-to-have but not mandatory.

Power Consumption, Heat Dissipation, and Cabinet Layout

The 1513-1 PN draws 24 V DC at approximately 0.7 A typical and 1.0 A peak, dissipating about 17 W. The 1512SP-1 PN draws 24 V DC at approximately 0.4 A typical and 0.6 A peak, dissipating about 10 W. The 1513's higher dissipation is due to the display and the additional X2 port hardware. Both CPUs require the System Power Supply on the S7-1500 rail (for the 1513) or the BaseUnit power (for the 1512SP) to deliver at least 1 A continuous at 24 V DC.

For cabinet layout, the 1513 station requires a minimum of 80 mm of clearance above and below the rail for ventilation. The 1512SP station requires 30 mm. The 1512SP can be mounted vertically (right-side up or upside down) without derating; the 1513 must be horizontal for the full temperature range (0 to 60 deg C), with vertical mounting limited to 0 to 45 deg C.

FAQ