Simulating Siemens LOGO! Master-Master Network Communication in Soft Comfort V8

Overview

Siemens LOGO! logic modules from generation 0BA7 onward support Ethernet-based peer-to-peer (master-to-master) communication. LOGO!Soft Comfort V8 introduced a dedicated Network Project view that lets engineers assemble multiple LOGO! programs into a single project, link them with a virtual Ethernet connection, and simulate the entire data exchange on a single PC without any physical hardware. The capability is essential for:

• Factory acceptance testing (FAT) of master-master topologies before deployment
• Classroom and WBT (web-based training) environments where two LOGO! devices are not available
• Continuous logic validation while one device is being serviced
• Verifying that NI/NQ and VM mapping tables are correct before firmware download

This article covers the complete procedure for configuring a master-master network project in LOGO!Soft Comfort V8, mapping network variables between the two peers, and enabling the network simulation engine. The procedure applies to:

• LOGO! 0BA7 hardware (6ED1052-1MD00-0BA7, 6ED1052-1HB00-0BA7, 6ED1052-1FB00-0BA7, and 230 RCE variants)
• LOGO! 0BA8 hardware (6ED1052-1MD08-0BA8, 6ED1052-1HB08-0BA8, and SIPLUS variants)
• LOGO!Soft Comfort V8.0, V8.1, V8.2, and V8.3 (and later service packs)

The network topology in this context is a flat Ethernet segment in which two LOGO! devices exchange digital and analog values using Network Inputs (NI), Network Outputs (NQ), and the Variable Memory (VM) area. Unlike the master-slave S7 connection that LOGO! supports, a master-master link treats both peers as equal participants; each device can publish NQs and subscribe to NIs independently.

Prerequisites

Before starting the simulation configuration, confirm the following hardware and software prerequisites.

1. LOGO!Soft Comfort V8.x installed on Windows 10 or Windows 11 (32- or 64-bit). Earlier V7.x releases do not contain the network project feature and cannot be used for this workflow.
2. Two LOGO! programs authored in Diagram mode (FBD). One is designated as the server, the other as the client. The role is logical only – both run the same protocol stack.
3. Both programs must target a LOGO! 0BA7 or 0BA8 device. Mixed-generation projects (for example, a 0BA6 combined with a 0BA8) are rejected by the network compiler.
4. Each program must declare the network variables it intends to exchange – NIs for inbound, NQs for outbound, and optionally VM words for analog values.
5. Administrator rights for the PC user account, because the simulator installs a virtual loopback adapter on first run and binds the local listening port.
6. A free TCP/UDP port range; LOGO!Soft Comfort uses high ports for the simulated network connection. No special firewall rules are required if the Windows Defender profile is set to Domain or Private.

Understanding the Network Project Concept

A Network Project is a container that holds two or more individual LOGO! programs plus the wiring between them. The container does not contain ladder or FBD logic itself – it only references child programs and defines how their NI/NQ/VM tags are interconnected. When you start simulation, LOGO!Soft Comfort loads every child program into its own virtual machine and executes them in parallel, exactly as if each was running on a separate physical LOGO! device.

The canvas displays two pin connectors (pin 1 and pin 2) representing the two LOGO! devices. The first program dragged into the canvas becomes the peer at pin 1; the second becomes the peer at pin 2. There is no implicit server/client role in the network layer itself – the role is defined by which side sends (NQ) and which side receives (NI) for a given tag.

Step 1: Create or Open Both Programs

1. Launch LOGO!Soft Comfort V8.
2. Open the first program (the server). Use File > Open and select the .lsc program file or a zipped .lsc project.
3. Open the second program (the client) in the same LOGO!Soft Comfort instance. The application supports multiple programs open simultaneously; each appears in its own Diagram editor tab.
4. Verify in Tools > Select Hardware that both programs target the correct device generation (0BA7 or 0BA8). If you intend to exchange analog values, ensure the device variant supports analog I/O or expansion modules.

If you only see one tab, you did not open both programs in the same instance. Close all programs, re-open them in a single LOGO!Soft Comfort session, and proceed.

Step 2: Switch to the Network Project View

1. From the View menu, choose Network Project, or click the Network Project page marker at the bottom of the workspace.
2. The canvas appears with two empty pin connectors and a toolbox on the left.
3. Confirm that the program tree on the left lists both of the open programs.

Step 3: Add the Programs to the Canvas

1. In the program tree, click and drag the first program (server) onto pin 1 of the canvas.
2. Click and drag the second program (client) onto pin 2 of the canvas.
3. Verify that both program icons show their diagram name and current firmware target (for example, 0BA8 Standard).

If only one program appears on the canvas, you did not have both programs open in the same LOGO!Soft Comfort session. Close the project, re-open both programs, and repeat the drag-and-drop sequence.

Step 4: Link the Two Masters

1. Click and hold pin 1 of the first program.
2. Drag the connection line to pin 2 of the second program.
3. Release the mouse button. A solid line between the two pins indicates a single Ethernet connection. LOGO!Soft Comfort V8 supports exactly one logical link between two masters in this view.
4. Double-click the connection line to open the Network Mapping dialog.

The Network Mapping dialog is the core of the configuration. It contains a table with the following columns:

Step 5: Map Network Variables

LOGO! 0BA7 and 0BA8 devices support three classes of network variables in peer-to-peer mode:

To map a digital state from Master A to Master B:

1. Set Source Tag to NQ3 of Master A (server program).
2. Click the direction cell and confirm the arrow points toward Master B (unidirectional, →).
3. Set Destination Tag to NI7 of Master B (client program).
4. Click Apply; the entry is now listed with an arrow icon.

To map a 16-bit analog value bidirectionally:

1. Set Source Tag to VW100 of Master A.
2. Set the direction to ↔ (bidirectional).
3. Set Destination Tag to VW100 of Master B.
4. Click Apply.

Click OK to commit the mapping. LOGO!Soft Comfort validates the entries; out-of-range addresses, mismatched data widths, or duplicate tag allocations are flagged in red and must be resolved before the project will compile.

Step 6: Enable the Network Simulator

Each program in the network must be put into simulation mode independently. This is the step most engineers miss the first time.

1. Open the first program (Master A) in Diagram mode by double-clicking its icon on the canvas.
2. Click the Simulation button in the toolbar (or press F3). The simulation toolbar appears at the bottom of the editor.
3. In the simulation toolbar, click the Network Link button (the chain link icon). When enabled, the icon turns blue and the status line shows Network: connected.
4. Click back to the canvas, then double-click the second program (Master B) to open it in Diagram mode.
5. Repeat the two clicks on Master B: Simulation button, then Network Link button.

At this point both LOGO! programs execute on the PC's virtual machine. The network connection is emulated over the Windows loopback adapter; no physical Ethernet cable is required. The cycle time is roughly 50 ms per program plus the network exchange overhead, so a full master-master round trip is typically 100 to 150 ms depending on the number of mapped tags and the host PC's load.

The simulation engine implements the same protocol stack as the firmware, so any logic that works in simulation will also work on the physical devices after download. Engineers can capture the traffic with Wireshark on the loopback interface (127.0.0.1) for protocol-level diagnostics if a mapping behaves unexpectedly.

Step 7: Verify the Simulation

After the simulation is running, perform the following acceptance checks:

1. Status indicators: Both program windows should show a green dot in the lower-right of the simulation toolbar. A red dot indicates the simulation is paused or has stopped due to a logic error.
2. Bidirectional digital exchange: Toggle an input on Master A and confirm the corresponding network input on Master B changes within one cycle (under 200 ms). Then toggle an input on Master B and verify the return path.
3. Analog propagation: Change a VW value in Master A's watch table; the same VW on Master B should reflect the change within two cycles.
4. Cycle counter check: Add an up/down counter (for example, B001) on the network input of Master B; the count should increment every time the corresponding NQ on Master A pulses.
5. Disconnect test: Click the Network Link button on one program to disable its side of the link. The other program should show a "Link down" message in the diagnostic window, and the inputs should freeze at their last value (default hold-last-value behavior).

If any verification step fails, proceed to the troubleshooting matrix below before modifying the mapping.

Troubleshooting Matrix

Firmware and Software Compatibility Matrix

LOGO!Soft Comfort V8 is forward-compatible with 0BA7 firmware ES (Engineering Status) 01 and later, and with 0BA8 firmware ES 02 and later. The following matrix summarizes the recommended pairings. Always verify against the System Manual of the installed firmware revision before deploying to production.

For hardware deployment, transfer the two programs to the physical LOGO! devices with Tools > Transfer > PC → LOGO!. The network mapping is downloaded as part of the program; no separate configuration step is required on the device itself. The IP addresses of the two physical devices must of course be set uniquely and belong to the same subnet as the engineering PC.

Best Practices for Field Commissioning

• Always run the simulation with the final compiled program before connecting to real hardware. The network simulator respects all function block timing, so logic bugs become visible before firmware flashing.
• Document the network mapping table inside the project comments – LOGO!Soft Comfort does not export the mapping as a separate document, and on-site engineers often receive only the .lsc file.
• Reserve the lowest VM addresses (typically VW0-VW15) for the LOGO! display and text objects. Start analog network exchange at VW100 or higher to avoid accidental display collisions.
• Add a watchdog timer in each master that resets all NQs if the network link has been down for more than 5 seconds. This prevents a stuck-on output if one device loses power mid-cycle.
• When upgrading firmware on a deployed 0BA7 or 0BA8, re-verify the network project in simulation first. Some ES revisions change the default listening port and require a configuration update in Tools > Ethernet Connections.
• Use a single subnet /24 (255.255.255.0) for the master-master link. LOGO! does not support routing across VLANs in V8 firmware; if you need a routed topology, terminate the master-master link at a managed switch on the same VLAN.
• Disable the LOGO! webserver on both devices when commissioning a master-master link. The webserver and the master-master protocol share the same Ethernet port and can starve each other of CPU cycles on the 0BA7.

Differences Between Simulation and Real Hardware

While the simulation engine is faithful to the firmware, a few behaviors differ and are worth knowing for FAT work:

• Cycle time: The simulator runs as fast as the host CPU allows (typically 20-50 ms per program). The physical 0BA8 device locks the cycle time to 250 ms; analog updates may therefore appear faster in simulation than in production.
• Network loss behavior: The simulator does not simulate packet loss, latency, or device reboot. Validate those failure modes by physically disconnecting the Ethernet cable on the real device.
• Power-on defaults: The simulator always starts with the program-defined initial values. The physical device honors the Retentivity setting per function block, which can mask bugs in the simulation.
• Display: The simulator shows the LOGO! display on the host screen; the physical device shows it on the integrated TDE. Verify any text or bar-graph that references network inputs on the actual TDE before sign-off.

Frequently Asked Questions