Siemens LOGO! Network Input and Output Configuration Guide

Siemens LOGO! 8 logic modules (6ED1052-xxxx-xBAx family) expose a feature that the older LOGO! generations did not: network inputs (NI) and network outputs (NO) carried over the on-board Ethernet port. NI/NO blocks let a local program read a digital state from a remote LOGO! or expose a local digital state to a remote LOGO! without writing S7 code, sending e-mails, or building a remote I/O island. The result is a flat, peer-to-peer shared I/O image across every LOGO! on the same IP subnet.

This reference walks through the exact configuration flow used to map I1 on LOGO! 1 (IP 192.168.0.2) to output Q1 on LOGO! 2 (IP 192.168.0.3), including the version-specific menu path inside LOGO!Soft Comfort V8.x, the project transfer checklist, and the field-proven troubleshooting matrix that resolves the "simulation works, hardware does not" or "symbol shows but Q1 does not change" symptoms that surface in most commissioning calls.

1. Network I/O Concept on LOGO! 8

LOGO! 8 ships with an on-board Ethernet interface (192.168.0.0/24 default) that supports up to 16 S7 connections. A subset of those connections is reserved for the LOGO!-to-LOGO! shared I/O mechanism. From a programmer's view:

• A Network Input (NI) block is a Boolean tag inside the local program whose value is read from a remote LOGO!'s digital output, marker, or network output.
• A Network Output (NO) block is a Boolean tag that the local LOGO! broadcasts to any peer that has mapped a corresponding NI to it.
• The transport is Siemens S7 communication over TCP/UDP port 102. No router, NAT, or VPN is involved; both peers must be reachable on the same Layer 2 broadcast domain.

The capacity limits (per the LOGO! 8 System Manual, 06/2021 edition, section 4.4) are:

Network I/O is fully bidirectional, so a single peer relationship can carry many NI/NO pairs. Each NI/NO is identified in the project by a 1-based index (NI1..NI64) and bound to a peer's IP plus a source/target tag.

2. Prerequisites

Before you open LOGO!Soft Comfort, confirm the following are in place. Skipping any of these is the single most common cause of "the block is red, value stays 0" during simulation.

2.1 Hardware

• Two or more LOGO! 8 base modules, each with firmware FS:04 (or later FS:05). Older FS:01-FS:03 firmware has NI/NO bugs that were corrected in FS04; check with the on-board menu LOGO! > Diagnostics > FW Version.
• Standard Cat5e/Cat6 Ethernet cabling to a common switch or direct crossover (modern NICs auto-MDIX; crossover is not strictly required).
• 24 V DC power supply sized for the LOGO! current draw (base module 12 V/24 V variants draw 1.2-2.4 W; see the rating plate).

2.2 Software

• LOGO!Soft Comfort V8.3 (or later) installed on the engineering PC. The project file extension is .lsc; V8.x projects are forward-compatible with newer V8 releases, but never save a newer-version project as an older version.
• Ethernet access from the PC to both LOGO! base modules. A ping 192.168.0.2 and ping 192.168.0.3 must succeed before you start configuration.

2.3 IP Addressing Plan

By default, every LOGO! 8 ships with IP 192.168.0.2. The first device on the network keeps the default; every additional device must be re-addressed to avoid an IP collision. A four-device example:

3. Project Setup in LOGO!Soft Comfort

1. Launch LOGO!Soft Comfort V8.3 and choose File > New. Select LOGO! 8 (0BA8) as the target device in the project tree.
2. Open Tools > Options > Ethernet Connections and add both peer IP addresses. The dialog caches the addresses used by the NI/NO configuration wizard.
3. Save the empty project as net_io_demo.lsc on a local drive (network shares can break the license check on older V8 builds).

4. Configuring the Network Output (Publisher Side)

The publishing LOGO! is the device that owns the physical input you want to share. In the example, LOGO! 1 at 192.168.0.2 owns I1 and must publish it as a network output.

4.1 Insert the NO Block

1. In the programming window, drag a Network Output (NO) block from the special-function palette onto a free rung. (Shortcut: type NO in the search box.)
2. Wire the block's input to a marker that mirrors I1. The simplest implementation is a direct assignment using a digital flag:\li>

Network 1:
  I1  ----[ NO1 ]----  (output side unconnected)
  |        ^
  |        |
  +-- B001 (feedback marker, optional)

3. Double-click the NO block to open the property dialog. Confirm:\li>

4.2 Declare the Peer in the NI/NQ Table

LOGO!Soft Comfort maintains a separate table that binds NO/NI blocks to peer IP addresses. Open it from Tools > NI/NQ Configuration (in some V8.x builds the menu label is Network Project > NI/NQ Table):

1. Click Add Peer and enter 192.168.0.3 (LOGO! 2's IP).
2. Under Local NO, select NO1. The Remote NI field on the peer side is informational only; the remote project is configured independently.
3. Click Apply. The peer line turns green if the destination IP is reachable from the engineering PC.

5. Configuring the Network Input (Subscriber Side)

The subscribing LOGO! is the device that should react to the published value. In the example, LOGO! 2 at 192.168.0.3 must turn on Q1 whenever the peer's I1 is high.

5.1 Insert the NI Block

1. Open the project for LOGO! 2 (or, in a multi-device project, switch the active target in the project tree).
2. Drag a Network Input (NI) block onto the rung that drives Q1:

Network 1 (LOGO! 2):
  NI1  ----( Q1 )

3. Double-click NI1. In the property dialog, fill in:

5.2 Save and Compile

1. Press F5 or use File > Compile > Compile All to rebuild the project. Any unresolved NI/NO references show in the message window as warnings (yellow) or errors (red).
2. Confirm that the message window reports 0 errors, 0 warnings. If you see "Reference to undefined NI/NO index", reopen the NI/NQ table and verify the index numbers match on both sides.

6. Transfer and Commissioning

1. Connect the PC to the switch that fans out to both LOGO!s. Verify reachability with ping 192.168.0.2 and ping 192.168.0.3.
2. Power on LOGO! 1 and LOGO! 2. Wait until the on-board display shows LOGO! ready (no Ethernet icon flashing red).
3. In LOGO!Soft Comfort, select Tools > Transfer > Transfer to Device. The dialog lists every reachable LOGO!; choose the device that matches the project (verify the serial number, not just the IP).
4. Repeat the transfer for the second project on the second LOGO!.
5. Switch both devices to RUN. The status bar should show Online: connected and the Ethernet icon on the on-board display should be solid green.

7. Verification

Three independent checks should pass before you sign off the system.

7.1 Online Monitor

Select Window > Online Monitor in LOGO!Soft Comfort. The NI1 block on the subscriber should track the NO1 block on the publisher with a latency between 80 ms and 200 ms. If the trace is flat, jump to the troubleshooting matrix below.

7.2 Physical Output Toggle

Force I1 on LOGO! 1 with a wire link (24 V on terminal I1) and measure Q1 on LOGO! 2 with a multimeter. The relay contact (or transistor output, depending on the LOGO! variant) should close within 200 ms.

7.3 LED Indicators

LOGO! 8 base modules with Ethernet have a dedicated LINK LED per port. Steady green = link up; flashing green = traffic. Steady off = cabling or IP mismatch. The RUN/STOP LED flashing red at 1 Hz means the program is in STOP due to a fault; flashing red at 2 Hz indicates a missing or unreadable micro SD card.

8. Troubleshooting Matrix

The following table maps the most common field complaints to root causes and corrective actions, drawn from the LOGO! System Manual and observed support cases.

9. Analog Network I/O (NAI/NAQ)

LOGO!Soft Comfort V8.2 and later also support Network Analog Input (NAI) and Network Analog Output (NAQ) blocks. They share the same NI/NQ table but carry 16-bit or 32-bit integer payloads. Use NAI/NAQ for sharing analog inputs (e.g., AI1 temperature on LOGO! 1) across the same Ethernet. The configuration flow is identical to digital NI/NO except that the block carries a numeric value; the receive side scales the value with the same gain/offset used on the publish side. See the LOGO! 8 System Manual, section 4.4.3.

10. Security and Network Hardening

LOGO! 8 ships with no password protection enabled by default. For industrial deployments, configure the following before the system leaves the commissioning site:

• Program access password. Tools > Options > Password. Set a non-trivial password to prevent upload of the LSC project.
• Network separation. Place the LOGO! subnet on a dedicated VLAN with no path to the corporate network. NI/NO traffic is unauthenticated.
• Disable unused services. On the on-board menu (LOGO! > Network > Services), disable the FTP server and Web server unless they are required for the application.
• Firmware updates. Periodically check the Siemens Industry Online Support portal for the latest LOGO! 8 firmware (currently FS05 as of the FS05 release note). Apply via micro SD card to avoid the network outage that the online update can cause.

11. Limits and Migration Notes

When you design a system that depends on network I/O, account for the following constraints, all of which are documented in the LOGO! 8 System Manual:

• Up to 8 LOGO! peers can be addressed by a single LOGO! base module. Exceeding this requires a CMR2020/CMR2040 router that adds its own peer slots.
• Total NI + NAI + NAI-word blocks cannot exceed the available program memory. The 0BA8 base module offers 8500 function-block words; NI/NO blocks consume one word each.
• Network I/O does not survive a power cycle in volatile mode. If the application requires the last published value to be restored after a brown-out, store the value in a retentive marker and re-publish it on the first RUN cycle.
• Mixing LOGO! generations is not supported. A LOGO! 8 cannot read NI/NO from a LOGO! 7 or 6 base module.

12. Frequently Asked Questions