Problem Overview
A common deployment failure when programming the Siemens LOGO! in LOGO! Soft Comfort is a transfer error in which the editor reports that a counter has "no output" and refuses to download the program to the controller. The program runs flawlessly in simulation mode on the PC, but as soon as the user selects PC → LOGO! (or clicks Transfer), the action is aborted by the information bar at the bottom of the Soft Comfort window.
Symptoms observed in the field:
- Simulation (F5 / toolbar Simulation button) works without warnings.
- Transfer (Tools → Transfer → PC → LOGO! or Ctrl+F8) is rejected.
- The information bar (the status strip below the diagram) displays a message indicating that the counter block has no output.
- The counter block in the diagram has no visible Q (digital output) connected to any other block, digital output marker, or flag.
- No hardware output (Q1 through Q4 / Q8 / Q16, depending on the base module) is wired to the counter's output terminal.
This condition is purely an editor-side rule, not a runtime fault of the LOGO! base module. It is therefore a logic and wiring problem inside the LOGO! Soft Comfort program, not a hardware, firmware, or communication fault.
Root Cause: Function Block Output Connectivity Rule
Every function block (FB) in LOGO! Soft Comfort that produces a digital result exposes a dedicated output terminal on the right-hand side of its block graphic. The standard counters in the toolbox fall into this category, meaning they are output-bearing function blocks. According to the LOGO! Soft Comfort Online Help and the Siemens LOGO! system manual, an output-bearing block must have its Q terminal connected to a target before the program can be compiled for the controller. The compiler will refuse to build a project for download whenever any Q terminal is left floating, even if the project simulates successfully.
The simulator relaxes this rule because it does not actually have to emit a binary to a discrete output driver. During PC simulation, the LOGO! Soft Comfort engine evaluates the block, but no physical Q line is required, since there is no real output relay. The transfer to the LOGO! base module, however, requires a complete wiring graph so that the firmware can map every block output to a real or virtual destination on the device.
Common design patterns that lead to this error include:
| Pattern | Why It Fails |
|---|---|
| Counter used purely as an internal accumulator, with the value displayed on a LOGO! TD/LOGO! TDE text panel only | Even when the count value is read via a display function, the counter's Q line still must be terminated — display tags do not consume the Q output. |
| Counter Q driving only an internal flag (M flag) but not the visible terminal of the block | The editor checks the schematic. The Q must visually be connected to a downstream block, output, or flag pin on the diagram. |
| Counter inserted from the toolbox before the rest of the diagram was built | Developers frequently drop a counter as a placeholder and forget to wire its output later. |
| User confused the input terminals (Trg, R, Cnt) with the output and only wired inputs | The counter only has one output terminal; it must be wired to a target. |
Affected LOGO! Hardware and Soft Comfort Versions
The behavior is consistent across the modern LOGO! 8 (BA0/BB0) and LOGO! 8.3 (BF0) families. Although the symptom has been documented for years, it still appears frequently in the field because the simulation and transfer paths have different validation rules.
| Hardware Family | Typical Order Number | LOGO! Soft Comfort Required |
|---|---|---|
| LOGO! 8 (BA0) | 6ED1052-1xx08-0BA0 (base), 6ED1055-1xx08-0BA0 (pure) | V8.0 or higher |
| LOGO! 8 (BB0) | 6ED1052-1xx08-0BA1 / 6ED1055-1xx08-0BA1 | V8.2 or higher |
| LOGO! 8.3 (BF0) | 6ED1052-1xx08-0BA2 / 6ED1055-1xx08-0BA2 | V8.3 or higher |
| LOGO! 8.4 (BG0) | 6ED1052-1xx08-0BA3 / 6ED1055-1xx08-0BA3 | V8.4 or higher |
| LOGO! 0BA7 (legacy 7th gen) | 6ED1052-1xx07-0BA0 | V7.x |
You can confirm the Soft Comfort release under Help → About LOGO! Soft Comfort. The installed release must be at least equal to the firmware on the target LOGO!. The transfer dialog will warn you if the project is intended for a newer firmware than the connected base module supports.
Counters in the LOGO! Toolbox
LOGO! Soft Comfort provides three standard counter blocks. Each one has its own output terminal requirements.
| Block (English / DE) | Inputs | Output | Output Behavior |
|---|---|---|---|
| Up/Down counter / Vor-/Rückwärtszähler | Trg (count), Rst (reset), Dir (direction), Par (parameter) | Q | Q = 1 when the count value reaches the parameterized threshold. |
| Up counter / Vorwärtszähler (older releases) | Trg, Rst, Par | Q | Q = 1 when the count has been reached. |
| Hours counter / Betriebsstundenzähler | En (enable), Ral (reset), Par | Q | Q = 1 when the hours threshold is exceeded. |
The Q terminal on each of these is mandatory. The Help view in Soft Comfort shows a small block diagram with a labeled Q; if the Help panel lists a Q line that is not connected in the diagram, that is the source of the transfer error.
Step-by-Step Solution
Follow this procedure to make the program transferable while preserving the original counting logic.
- Open the project in LOGO! Soft Comfort and switch from Simulation back to Diagram Editor.
- Locate the counter block in the diagram. It will be labeled with the counter symbol (the three-block compound icon) and a block number such as B003.
- Click the Q terminal on the right-hand side of the counter block. The cursor becomes a small connector.
-
Drag the wire to one of the following legitimate destinations:
- A digital output on the base module (Q1, Q2, Q3, Q4) — for example, a relay or transistor output driving a lamp, contactor, or indicator.
- An internal flag (M1 … M64, depending on firmware) — useful when the count event is consumed only by other blocks.
- Another function block's input (such as the enable of a second counter, the set input of a flip-flop, or the input of a pulse generator).
- An output of an I/O expansion module, e.g. Q5 through Q16 of a DM8 or DM16 module.
- Release the mouse to commit the wire. The Q terminal will now show a solid connection line.
- Repeat for any other counter block that has an unconnected Q terminal.
- Re-attempt the transfer using Tools → Transfer → PC → LOGO! (or the toolbar Download button). The information bar should no longer report the error.
Information Bar Messages You May See
The bottom information bar in LOGO! Soft Comfort outputs short diagnostic messages. Mapping the most common ones to actions speeds up debugging:
| Information Bar Text (EN) | Cause | Corrective Action |
|---|---|---|
| The block has no output. | Q terminal of a counter, timer, or other output-bearing FB is unconnected. | Wire the Q terminal to an output, flag, or downstream block input. |
| The output is already used by another block. | Two blocks share a hardware output Qx or a flag. | Reassign to a free output/flag, or remove the duplicate consumer. |
| No connection at input / Input not connected. | An FB input (Trg, En, Rst, etc.) is dangling. | Wire the input, or set a constant if the block allows a constant default. |
| The block is not allowed in this LOGO! firmware. | Block is only available in newer LOGO! releases (e.g., analog filters in 0BA6+). | Match Soft Comfort project to target firmware, or replace block with a simpler equivalent. |
| Block memory exceeded / Maximum number of blocks exceeded. | The configured base module has reached its block budget (LOGO! 8 supports up to 400 blocks, 0BA7 supports 130/200/250). | Reduce the number of FBs, or upgrade the LOGO! base module. |
| Transfer aborted: Communication error. | USB/Ethernet link or COM port issue; not related to wiring. | Check the Ethernet cable, LOGO! IP, firewall, USB driver, and that the LOGO! is in transfer mode (ESC + arrow key in older releases). |
Simulation vs. Transfer — Why They Behave Differently
LOGO! Soft Comfort's simulation is a purely software event chain: the engine simply evaluates each FB and propagates signals. The diagram validator that runs before a transfer is a separate, stricter pass that walks the schematic and enforces the "every output-bearing block must have a connected Q" rule. The two processes share data but are not equivalent, which is why a project can simulate cleanly and still fail to download. The same gap also applies to the offline / online comparison dialog and the block list export; these all pass through the same validator.
Best practice: after any editing session, run Tools → Validate Project (in recent releases) or Diagram → Check to force a pre-transfer validation. This catches unconnected outputs before you waste a transfer attempt.
Alternative Internal Counter Implementations
If you need a counter purely for internal use (no external output, only feeding downstream logic) and want to keep the wiring diagram minimal, you can:
- Drive Q to a flag (M1..M64) instead of a hardware output. The counter still produces a Q signal, but the flag is the consumer. Other FBs read that flag through a digital marker input.
- Read the count value via the UDF/anonymous variable using the Read analog value or Display value block — for the LOGO! TDE 6-inch text panel, you can also display the live count value using the counter's parameter reference without ever wiring Q.
- Use a self-resetting on/off delay pattern combined with an up counter if your goal is "count pulses until a threshold, then continue counting." In all cases, the counter's Q must still be connected to something for the program to transfer.
- Promote to LWE (LOGO! Web Editor) variables in 0BA8+ projects: expose the count value as a network variable (VN), which can be read by a remote HMI. The counter's Q is then driven by a flag that the Web Editor script polls.
Verification
- Run offline simulation (F5). Cycle the count input and confirm the counter increments, the threshold triggers Q = 1, and any downstream devices or flags respond.
- Re-check the information bar for warnings. It should remain clear of any "no output" messages.
- Connect to the LOGO! base module using Tools → Connect. Confirm the firmware matches the project (for example, LOGO! 8.3 - 0BA2).
- Transfer the program (Ctrl+F8). A successful transfer dialog will appear with a checksum and a "Transfer completed successfully" message.
- Switch the LOGO! to RUN mode. The home screen should display Stop → Run, and the green RUN indicator should be lit.
- Test the input that drives the counter (digital input, network tag, or simulated HMI button). Verify the Q output triggers the expected load, indicator, or downstream block.
- Use online test (Tools → Test) in Soft Comfort to monitor the live state of the counter and the connected flag or output, confirming that the wiring is correct end-to-end.
Troubleshooting Matrix
| Symptom | Likely Cause | Action |
|---|---|---|
| Information bar: "no output" | Counter Q unconnected | Connect Q to output/flag/FB input |
| Sim OK, transfer fails with same error | Sim and validator differ | Always satisfy validator rule (connect Q) |
| Block Q visible but transfer still fails | Output already used elsewhere | Check the output list, move consumer to free Q or M flag |
| Multiple counters fail to transfer | Several unwired Qs | Loop through all output-bearing blocks |
| Same program transfers on a different LOGO! | Different block count limits | Compare block budgets in LOGO! Settings |
| Transfer dialog opens but no progress | Wrong IP / port / firewall | Verify IP in Soft Comfort matches LOGO! ESC → Network settings; check UDP 1024 / TCP 102 default |
FAQ
Why does the counter simulate but not transfer in LOGO! Soft Comfort?
Simulation skips the strict diagram validation that runs at transfer time. If the counter's Q terminal is unconnected, simulation still runs, but the transfer validator aborts the download. Connect the Q terminal to a digital output, internal flag (M1..M64), or downstream function block input.
Can I use a LOGO! counter without ever driving a physical output?
Yes — drive the counter's Q to an internal flag (M) and consume that flag from other blocks or from a text display. The Q must still be wired in the diagram, but the destination can be virtual rather than a physical relay or transistor output.
Which LOGO! Soft Comfort versions support the modern counter blocks?
LOGO! Soft Comfort V8.0 supports LOGO! 8 (BA0); V8.2 supports BB0; V8.3 supports 8.3 (BF0); V8.4 supports 8.4 (BG0). Always match the Soft Comfort release to the firmware on the connected base module to avoid transfer rejections.
The information bar says "block has no output" but my diagram has a Q line — what is wrong?
The Q line may be wired to a comment, text, or an unassigned output pin. Hover over the wire; if both ends do not resolve to a real connector, redraw the connection. Also verify that the Q is not a duplicate of another block's output on the same Qx or M flag.
How do I check the maximum number of blocks allowed on my LOGO!?
Open Tools → LOGO! Settings in Soft Comfort. The dialog reports the connected device family and the block budget (up to 130, 200, 250, or 400 blocks depending on the 0BA generation and base module). If you exceed this, the validator will block the transfer.