Resolving Siemens LOGO! 8 FS04 Program Load Failure with LOGO!Soft Comfort V8.1

A Siemens LOGO! 8 base module responds to ARP/ICMP echo, shows up in the LOGO!Soft Comfort "Accessible Nodes" discovery, accepts the default password, and refuses to download any program. The headline cause is a mismatch between the device hardware functional state (FS04) and the engineering tool version. The variant printed on the rating label — not the marketing colour or the order number alone — determines which LOGO!Soft Comfort (LSC) revision is required. A V8.0 installation cannot stage a program onto a LOGO! 8.FS04 even though the Ethernet discovery succeeds. The required corrective action is to upgrade the engineering software to LSC V8.1 (or later), confirm the target selection in the project tree, and re-verify the physical layer and the power supply budget. The rest of this reference details the diagnostic flow, the LSC version map, the network parameters, the power supply rules, and a verification matrix for the field engineer.

1. Overview of the Failure Mode

The symptom is consistent across multiple field reports: a brand-new LOGO! 8 base module is wired, powered, and reachable on TCP/IP. LOGO!Soft Comfort scans the subnet, the device appears with its MAC address (for example E0-DC-A0-1A-CC-C9), and the connection test in the "Accessible Nodes" dialog returns "Yes". A click on the device opens the password prompt, the default password LOGO is accepted, and the session negotiates. The user then attempts PC → LOGO! (download), and either the transfer hangs, the project tree shows no compatible target, or the tool reports that no program slot is writable. Reinstalling the same V8.0.x build does not change the outcome. Three classes of cause are usually present together, and they must all be addressed:

1. Functional state mismatch — the LOGO! 8 is a FS04 device and the installed LSC is V8.0.
2. Power supply under-budget — a 12 VDC 500 mA wall adapter is insufficient when expansion modules are stacked or when Ethernet is active during the program transfer.
3. Default gateway / subnet inconsistency — the LOGO! 8 has gateway 223.0.0.0 while the PC has a different gateway or no gateway. This rarely blocks local traffic, but it does indicate that the IP parameters were edited and not reset to factory defaults.

2. Identifying the LOGO! 8 Hardware Functional State

Siemens ships the LOGO! 8 platform in successive functional states (FS). The functional state is a firmware/hardware release identifier stamped on the rating label of the base module and embedded in the device's hardware identifier string. The marketing designation "LOGO! 8" refers to the entire 0BA8 generation. The functional state is the field that matters for engineering-tool compatibility.

2.1 Locating the FS code on the device

Open the hinged flap on the front of the base module. The rating label is printed on the inside of the housing or on the side. Read the line that begins with the order number (for example 6ED1052-1MD08-0BA1) and the line below it that lists the firmware release and functional state. The functional state is the two-character suffix after the FS designator, e.g. FS:04. Some early 0BA8 modules carry FS:01 through FS:03; modules with FS:04 and later are functionally compatible with LSC V8.1 and newer.

2.2 Functional state vs marketing designation

3. LOGO!Soft Comfort Version Requirements

LOGO!Soft Comfort is the engineering environment used to program, simulate, and commission the LOGO! 8. The tool version determines which hardware functional states are addressable in the project tree. The mapping is enforced by the LSC project wizard: when the user picks the target device, only the FS revisions that the tool knows about are listed in the device dropdown.

3.1 LSC version map

3.2 Why V8.0 cannot reach a FS:04 device

The LSC V8.0 project tree does not list the FS:04 device class. The download path therefore cannot negotiate a target FS that V8.0 does not know. The Ethernet session opens — the LOGO! 8 still speaks the same TCP/IP and S7-compatible protocol — but the program slot is not writable from the older tool. Installing V8.0 on top of itself does not change the device table; only a V8.1 (or later) installation unlocks the FS:04 target.

3.3 Where to obtain the upgrade

Siemens publishes the demo, upgrade, and full releases of LOGO!Soft Comfort on the official product page. Use the Siemens Industry Online Support portal or the product support download center. Do not obtain the engineering tool from third-party mirrors. The full version requires a license key; the demo version is fully functional for upload, download, and online test for 30 days.

Reference: Siemens Support — LOGO!Soft Comfort V8.x downloads (entry ID 109751784)

4. Network and IP Configuration

The default IP parameters of a factory-fresh LOGO! 8 base module are shown below. A user-edited configuration that drifts from these defaults is not by itself a fault, but a non-default gateway in a single-segment network is a strong indicator that the IP menu on the device was touched with insufficient context.

4.1 Factory defaults (LOGO! 8 BM with Ethernet)

4.2 PC-side IP requirements for a direct connection

When the PC is connected to the LOGO! 8 without a router, set the PC NIC to a static address in the same /24 subnet. The most common working configuration is:

• PC IPv4: 192.168.1.101
• PC subnet: 255.255.255.0
• PC gateway: 192.168.1.254 (or left blank for direct attach)
• LOGO! 8 IPv4: 192.168.1.103
• LOGO! 8 subnet: 255.255.255.0
• LOGO! 8 gateway: 192.168.1.254

4.3 Inline topology diagram

4.4 Validating the link

1. From the PC command prompt: ping 192.168.1.103. Expect four replies with TTL in the 64–128 range.
2. From the PC: arp -a | findstr 192.168.1.103 to confirm the MAC matches the label.
3. In LSC: Tools → PC/LOGO! → Connect or open Accessible Nodes. The device should appear with status "Yes".

5. Power Supply Considerations

A 12 VDC 500 mA wall adapter (6 W total) is at the lower edge of what a LOGO! 8 base module with Ethernet can sustain. The base module alone draws approximately 1.5–2.0 W with Ethernet active; each digital expansion (DM8) adds about 0.5–1.0 W, and each analog expansion (AM2 / AM2 AQ) adds another 1–1.5 W. During a program transfer the Ethernet PHY and the internal flash controller both ramp up, and the inrush can momentarily exceed the steady-state budget of a small adapter.

5.1 Power budget rule of thumb

For a 12 VDC variant, scale the current budget by 2× (i.e., a 500 mA 12 VDC supply ≈ 250 mA at 24 VDC equivalent and is marginal for anything beyond the bare base module). For reliable program transfers and field expansion headroom, use a regulated 24 VDC supply rated at 2.5 A or higher. The Siemens LOGO! Power 24 V / 2.5 A DIN-rail supply is the recommended match.

5.2 Symptoms of an under-sized supply

• LOGO! 8 boots, the LCD shows LOGO! 8 ... for several seconds, then resets.
• Ethernet link is up briefly, then drops during program transfer.
• Discovery succeeds ("Yes") but the download fails with a timeout.
• The supply voltage at the LOGO! terminals droops below 10.5 V (12 V variant) or 20.4 V (24 V variant) under load.

6. Default Password and Access Protection

LOGO! 8 base modules prompt for a password on every TCP connection. The factory default password is the literal string LOGO (case-sensitive, no quotes, no leading/trailing spaces). A connection that prompts for a password and accepts LOGO confirms two facts: the device is reachable on the S7 port, and the user-supplied password matches the stored value.

7. Step-by-Step Resolution Procedure

Follow this sequence to clear the failure mode. Each step has a deterministic verification, and a clean run produces a successful program download.

7.1 Prerequisites

• Windows 10 / 11 PC with administrator rights.
• Ethernet cable (CAT5e or better), preferably a direct patch to rule out switch issues.
• 24 VDC / ≥ 2.5 A regulated supply wired to the LOGO! 8 power terminals (L+, M).
• Access to the LOGO! 8 rating label to confirm the FS code.
• Siemens Support login for the LOGO!Soft Comfort download.

7.2 Procedure

1. Confirm the functional state. Power the module, open the front cover, and read FS:XX from the label. If the code is FS:04 or higher, continue. If the module is FS:01–FS:03, the original V8.0 tool is correct — investigate the network and supply next.
2. Verify the power supply. With a DMM, measure the DC voltage at the LOGO! 8 L+ and M terminals under load. Replace any 12 VDC 500 mA adapter with a regulated 24 VDC 2.5 A supply.
3. Reset the LOGO! 8 IP parameters to factory defaults from the device menu: Network → IP Address → 192.168.1.103; Network → Subnet Mask → 255.255.255.0; Network → Gateway → 192.168.1.254. This clears any user-edited 223.0.0.0 mis-entry.
4. Connect the PC directly with a CAT5e patch. Disable Wi-Fi on the laptop to remove the default route from the route table. Set the PC NIC to 192.168.1.101 / 255.255.255.0, no gateway or 192.168.1.254 if a switch is present.
5. Allow LOGO!Soft Comfort through the firewall in Windows Defender. Add an inbound rule for %ProgramFiles%\Siemens\LOGO!Soft Comfort\V8\LogoSoftComfort.exe on UDP/TCP ports 102, 5005, and the broadcast range 49152–65535.
6. Install LOGO!Soft Comfort V8.1 (or later). The installer is signed by Siemens AG; verify the publisher before running. Activate with a valid license key or run the 30-day demo for evaluation.
7. Open or create a project and set the target to LOGO! 8.FS4 in the device dropdown. The dropdown in V8.1 explicitly lists "LOGO! 8.FS4"; in V8.0 it does not.
8. Run PC → LOGO! (Download). When prompted for the password, enter LOGO. The status bar should report "Transfer complete".
9. Switch the LOGO! 8 to RUN using the device's STOP/RUN button. The green RUN LED illuminates and the program begins executing.

7.3 Verification checklist

8. Troubleshooting Matrix

The matrix below maps the most common observed symptoms to root cause and corrective action. Use it as a triage table before deeper diagnosis.

9. Online State Transitions

Understanding the protocol state machine clarifies why discovery can succeed while a program transfer fails. The diagram below is a simplified view of the S7/LOGO! communication handshake.

The first three transitions (discovery → connect → password) succeed regardless of LSC version because they are network-layer and password-layer operations. The write request at the application layer is where the FS gate is enforced. An LSC V8.0 client cannot produce a write PDU that the FS04 firmware accepts, so the transfer aborts after the session is already established. This is the canonical explanation for "Yes in Accessible Nodes, but no download".

10. Notes on Direct PC vs Router Attachment

A switch or router between the PC and the LOGO! 8 does not break communication, but it adds three failure modes the field engineer must rule out:

1. VLAN tagging — if the PC port is on a tagged VLAN that the LOGO! 8 cannot interpret, the broadcast-based discovery will fail. Use an untagged access port for both ends.
2. Spanning-tree delay — when the link comes up, IEEE 802.1D STP can hold the port in blocking/learning for 30–50 s. During this window, LSC will not see the device. Enable port-fast (or the vendor equivalent) on the access port.
3. DHCP relay / helper — the LOGO! 8 is a static-IP device; a DHCP server in the path does not assign it an address, but a relay can interfere with broadcast discovery. Disable DHCP relay on the access VLAN or set the PC NIC to a static address in 192.168.1.0/24.

For a first-time bench bring-up, always use a direct patch between the PC and the LOGO! 8. Once the program is loaded and the device is verified to run, the unit can be moved to the production switch.

11. Common Pitfalls

• Trusting "0BA8 Standard" as a sufficient identifier — it is not; the FS code on the label is the deciding field.
• Re-installing the same LSC V8.0.x build and expecting FS04 to appear in the dropdown — it never will.
• Using a 12 VDC 500 mA wall wart on a stacked base+expansion configuration — the supply droops and the module brown-outs during the flash write.
• Leaving the gateway at 223.0.0.0 — that is not a valid host in a /24 and indicates a prior mis-entry in the on-device IP menu.
• Blocking the S7 port in Windows Defender — the discovery may still appear to work for a single ping cycle, but the program transfer requires TCP/102 to be open.
• Mixing two devices at the default 192.168.1.103 on the same broadcast domain — only one will respond; the other is silent until its IP is changed.

12. Related Manuals and Official References

The following official Siemens documents are the primary reference set for the engineer working on LOGO! 8 commissioning:

• LOGO! 8 System Manual (6ED1050-1AA00-0AE8) — entry ID 109751784
• LOGO! 8 Product Information (FS:04 release notes) — entry ID 109741100
• LOGO!Soft Comfort V8.1 Online Help and Release Notes — entry ID 109766453
• Siemens LOGO! product page (siemens.com/logo)