WinAC RTX vs S7-1500 Software Controller: Selection and Migration Reference

Siemens offers two distinct PC-based control platforms that engineers frequently confuse: WinAC RTX (a software PLC running on a Windows host with the RTX real-time extension) and the S7-1500 Software Controller (CPU 1505S / CPU 1507S, a virtualized controller executed on a Siemens IPC or ET 200SP Open Controller). This reference consolidates the official Siemens product documentation, the support article 6SE27212 — PC-based Automation: S7-1500 Software Controller or WinAC RTX, and field commissioning experience to clarify when to select each platform, how to configure it inside TIA Portal, and how to migrate existing WinAC RTX applications to the newer S7-1500S target.

1. Overview: Two Generations of Siemens PC-Based Control

Both products replace a hardware S7 CPU with a deterministic control runtime executed on an industrial PC. They differ in architecture, supported engineering tool, IPC compatibility, and lifecycle status.

For new designs, the S7-1500 Software Controller is the recommended PC-based target. WinAC RTX remains supported only for installed-base migration, not for greenfield projects.

2. WinAC RTX Architecture

WinAC RTX is implemented as a Windows user-mode process that uses the RTX real-time subsystem (kernel driver) to schedule the PLC scan deterministically outside the Windows kernel. Components are:

• WinAC RTX kernel — IntervalZero RTX-based real-time scheduler.
• SoftPLC runtime — S7-300/400 instruction set, OB/FB/FC/DT organization.
• WinAC ODK — C/C++ interface for Windows-side data exchange with the real-time task.
• Softnet/PROFINET IO driver — for fieldbus connection through CP 1616/CP 1623/CP 1604.
• WinAC Panel — diagnostics view inside the Windows tray.

3. S7-1500 Software Controller Architecture (CPU 1505S / 1507S)

The S7-1500 Software Controller is delivered as a Siemens-installed Windows image on an approved IPC. The PC boots into a hypervisor (Siemens VMM) that hosts two virtual machines:

1. Windows VM — engineering tools, HMI, databases, OPC UA clients.
2. Controller VM — runs the S7-1500S firmware (CPU 1505S or 1507S) with the full S7-1500 instruction set, web server, trace, OPC UA server, and integrated PROFINET/PROFIBUS interfaces (where fitted).

The Controller VM is licensed with a USB license key (CoL — Certificate of License) or, in current deliveries, a software-based license (Wibu-Systems CodeMeter). The VM boots only if the IPC platform is recognized by the hypervisor — third-party PCs are deliberately rejected.

4. Approved IPC Platforms and Hypervisor Requirements

CPU 1507S is certified for a closed list of Siemens IPCs. Installing it on a third-party PC is technically blocked by the Siemens VMM: if the platform is not on the whitelist, the Controller VM does not start and reports a platform-mismatch diagnostic. Approved families per the SIMATIC IPC product portfolio and the entry ID 62521281 include:

• SIMATIC IPC227G / IPC277G (Nano/Panel)
• SIMATIC IPC427D / IPC477D
• SIMATIC IPC627D / IPC677D
• SIMATIC IPC647D / IPC677D
• SIMATIC IPC847D
• SIMATIC IPC1047 / IPC RW-545 (high-end rack PC)

Hardware revisions are critical: a CPU 1507S firmware image is paired with a specific hypervisor release that recognises a specific BIOS/firmware version of the IPC. When the IPC firmware is updated (BIOS, BMC, chipset microcode), the hypervisor driver set must be reinstalled from the matching SIMATIC S7-1500 Software Controller & SIMATIC IPC image DVD.

5. Licensing and Order Numbers

Both products are licensed, not sold as plain media. The user obtains the software only bundled with a license (per CPU slot) or as a pre-installed IPC bundle.

Engineers should confirm the current Siemens catalog (Industry Mall) for exact order numbers; revision numbers and bundling are subject to change with each TIA Portal release.

6. Configuring the S7-1500 Software Controller in TIA Portal

The following procedure assumes the IPC is delivered with the Siemens pre-installed image. Custom installations are not supported.

6.1 Prerequisites

• SIMATIC IPC with CPU 1507S bundle (Windows + Controller VM + hypervisor image installed by Siemens).
• TIA Portal V16 or later (matching the S7-1500S firmware version installed on the IPC).
• Valid S7-1500 Software Controller license (CodeMeter container or USB CoL).
• PROFINET/Ethernet cabling between IPC port and engineering PG/PC.
• PROFINET device names for any distributed I/O to be attached.

6.2 Step-by-Step Commissioning

1. Boot the IPC. Verify the hypervisor splash screen appears, then the Windows VM. The Controller VM boots in parallel and exposes its PROFINET interface as a Windows-bound network interface (alias Siemens CP 1605 or similar).
2. Assign IP addresses. Set the IPC's engineering port (X1/X2) to a fixed IPv4 address on a subnet the TIA Portal PG can reach (e.g. 192.168.0.10 / 255.255.255.0).
3. Open TIA Portal → Project view → Add new device → Controllers → SIMATIC S7-1500 → CPU 1507S. Match the order number / firmware version to the one installed on the IPC.
4. Configure the PG/PC interface in TIA Portal to use the Intel/PROFINET adapter that bridges to the Controller VM. Use Accessible nodes to confirm the controller is online.
5. Download the hardware configuration (right-click the device → Download to device → PG/PC interface). The Controller VM restarts; verify in the WinAC Panel / S7-1500S Tray that the project is in RUN.
6. Activate the license. Start the Automation License Manager on the Windows VM, transfer the CodeMeter license to the local container, restart the Controller VM. Without an active license the controller runs in demo mode for one hour per boot.
7. Configure the PROFINET topology (IO devices, device names, IP addresses) and download again.
8. Run the OB1 / cyclic task in RUN, verify the scan time with Online & Diagnostics → Cycle time. Compare against the configured minimum cycle time.

7. Configuring WinAC RTX (Reference for Installed Base)

For projects that are still on WinAC RTX 2010 (STEP 7 V5.x or TIA Portal with WinLC RTX target):

1. Install Windows, then install IntervalZero RTX before installing WinAC RTX. The RTX setup requires a reboot and creates the RTX kernel driver.
2. Install WinAC RTX 2010 (and F-runtime if applicable). Plug the USB license key.
3. Open the RTX Configuration Tool: assign one CPU core to the RTX scheduler exclusively, disable power management.
4. In STEP 7 / TIA Portal, add SIMATIC WinLC RTX as the PC station. Configure the PROFINET interface (CP 1616/CP 1623) and download the project.
5. Use WinAC Panel to verify RUN/STOP, diagnostic buffer, scan time, and I/O status.

8. Communication: PC-Based Controller as Master, S7-300/400/1500 as Slaves

Both products can act as a PROFINET IO controller or as an S7-communication client/server for connected SIMATIC PLCs. The most common configuration is a soft PLC on the IPC driving one or more S7-1500/S7-300/S7-400 stations over PROFINET or industrial Ethernet.

8.1 Protocols Available

8.2 Typical Slave Configuration (S7-1500 as Slave, PC-Based Controller as Master)

1. Add the S7-1500 CPU in the TIA Portal project as a separate device. Configure it with its own IP address on the same PROFINET subnet.
2. In the PC station's Devices & Networks view, drag a PROFINET IO connection from the soft PLC's PROFINET interface to the S7-1500's PROFINET interface.
3. For S7 communication, open Instructions → Communication → S7 Communication in the soft PLC program. Use PUT/GET blocks with the partner IP, rack, slot, and connection resource ID.
4. On the S7-1500 slave, allow remote access: Properties → Protection & Security → Connection mechanisms → Permit access with PUT/GET from remote partner.
5. Verify with Online & Diagnostics → Connection diagnostics. The connection status must show Established and the bytes transferred must match the configured send/receive area.

9. Migration from WinAC RTX to S7-1500 Software Controller

Siemens does not provide a one-step migration tool. The supported procedure is a manual port of the program logic, copy/paste of code blocks, and re-licensing. The entry ID 62521281 confirms that a direct device change or symbol export from WinAC RTX to CPU 1507S is not supported.

9.1 Migration Procedure

1. Open the original WinAC RTX project in TIA Portal (or STEP 7 V5.x with source export).
2. Create a new project. Add SIMATIC S7-1500 → CPU 1507S as the target device.
3. Map the hardware. Replace CP 1616/CP 1623/CP 1604 with the integrated PROFINET interface of the Controller VM. Map WinAC RTX-specific I/O (soft-PLC slot I/O) to the actual distributed I/O configured on the new IPC.
4. Copy OB1, OB35, OB82, OB100, OB102 from the source to the target. The block numbers and execution semantics are preserved because the S7-1500S firmware supports the classic OB set.
5. Copy FCs and FBs one at a time. Resolve differences:
   • Instance DBs: re-create the DBs as global/instance DBs in the S7-1500S target. Renumbering is recommended because S7-1500 supports a larger DB address space.
   • Re-entrant FBs (multi-instance): verify multi-instance capability. Some WinLC RTX libraries use single-instance patterns that need restructuring.
   • Retentive memory (REMAN / remanence): the WinAC RTX's persistent memory is stored in a Windows file. S7-1500S uses the standard S7-1500 retentive load memory (NV-RAM). Map every REMAN variable to a configured retentive area; otherwise values are lost on power down.
   • Libraries: WinAC-specific libraries (ODK, RTX extension blocks) must be replaced by S7-1500 equivalents. Custom C/C++ ODK code must be ported to the OPC UA server or to a separate Windows application using the S7-1500S OPC UA interface.
   • Time-of-day / clock: WinAC RTX uses Windows time unless a CP is fitted. S7-1500S has its own time-of-day clock and supports NTP and SIMATIC time synchronisation; rewrite any custom clock handling.
6. Re-create HMI tags and WinCC connections. The OPC UA namespace, tag names, and panel design will be redone.
7. Commission the new IPC, download the project, validate cycle time, retentive behaviour, and S7 connections side by side with the old WinAC RTX for at least 72 hours before cutover.

9.2 What Cannot Be Migrated

• Windows-side ODK C/C++ code written for the WinLC RTX API — these calls are not present in the S7-1500S firmware. The replacement path is OPC UA on the controller side and a C#/Python client on Windows.
• Reusable libraries of WinLC RTX type — they have no S7-1500 equivalent and must be re-implemented.
• Non-Siemens safety components configured in the WinAC RTX F project — must be re-validated on CPU 1507S F with PROFIsafe.

10. Comparison Summary Table

11. Field-Proven Caveats and Diagnostics

11.1 Demotion to Demo Mode

If the CodeMeter / CoL license is missing, the S7-1500S will start in demo mode for one hour per boot and then transition to STOP. The diagnostic buffer shows License missing or invalid. Remedy: install the CodeMeter container from the Automation License Manager, transfer the license, and reboot the Controller VM.

11.2 Platform Mismatch at Boot

The Controller VM does not start if the IPC firmware is newer than the hypervisor supports. The Siemens VMM logs the event in the Windows event log under Siemens VMM → Platform validation. Remedy: install the matching IPC firmware baseline from the pre-installation image DVD, or use the same DVD for both Windows and the Controller VM.

11.3 PROFINET Watchdog Trips

If the Controller VM is overloaded (CPU core assigned to Windows VM instead of the controller), PROFINET IO devices drop with IO device failure and the controller enters STOP with PROFINET IO — Watchdog timeout. Remedy: re-assign the core affinity in the hypervisor settings and disable C-State in BIOS.

11.4 Remanent Memory Loss

Programs migrated from WinAC RTX to S7-1500S frequently lose the REMAN attribute on the first cold start. Variables tagged REMAN in the WinLC project are not automatically marked Retain in the S7-1500S target. The diagnosis appears as 0 values in the process tags that previously held last-state data. Remedy: explicitly configure retain in the DB properties of the S7-1500S target.

11.5 Communication with Older Slaves

S7 communication with S7-300/400 slaves works, but the S7-1500S default firewall blocks PUT/GET access. The CPU must be configured with Connection mechanisms → Permit access with PUT/GET from remote partner = enabled on every S7-1500 slave in the network. Without this, PUT/GET blocks return STATUS = 0x80D3 (No connection established).

12. Verification Checklist After Commissioning

• Controller VM is in RUN, scan time within configured limit (check via Online & Diagnostics → Cycle time).
• License is active (Automation License Manager shows the license on the local container).
• PROFINET IO devices are in Data exchange state, no device shows Station failure or Diagnosis available.
• S7 connections to S7-300/400/1500 slaves show Established in the connection diagnostics.
• OPC UA server endpoint is reachable; test client (e.g. UaExpert) reads and writes the configured tags.
• Retentive data survives a power cycle of the IPC.
• Windows VM reboot does not stop the Controller VM (hypervisor protection verified).