Siemens STEP 7 FB Parameter Decoder: UEBW, STBE, STME, ZEIT

Overview

Siemens STEP 7 documentation and on-sheet (FUP/KOP/AWL) FB diagrams written by German-speaking engineers frequently use compact uppercase abbreviations that look opaque to anyone working from a translated interface. A block named stoerung with inputs UEBW, STBE, ZEIT and an output STME is a classic example. The same project also exposes timer symbols with TV, BI, DE, RV, Q and compare blocks with operands like DW1, FW16, and bit flags such as F163.1.

This reference decodes those abbreviations, maps the German terminology back to the underlying STEP 7 / IEC 61131-3 concept, and provides a repeatable workflow for engineers who inherit German-language S7-300/400 or S7-400 projects. It also covers the data/flag memory model used in classic STEP 7 so the decoded names can be cross-referenced against offline blocks and online monitoring views.

Prerequisites

1. STEP 7 (classic) or STEP 7 Professional with the project file (.s7p) or archived (*.zip) source available.
2. Access to the symbol table (S7-Program\Symbols) and the FB source in the offline program blocks folder.
3. Online connection to the CPU, or an offline STL/FBD printout of the FB.
4. Knowledge of the project base language: German, English, French, or mixed. Mixed projects are common in multinational plants.
5. Browser or desktop access to a translation tool such as Google Translate or Microsoft Translator for rapid gloss lookup.

Siemens STEP 7 Block Notation Background

STEP 7 follows the IEC 61131-3 PLC programming standard but retains a German heritage from the SIMATIC S5 lineage. Two naming conventions appear in parallel:

The on-sheet FB 205 named stoerung shown later in this article mixes both: the block name is symbolic (German word), while the operands on its connections (OFF, S36, horn, F173.6) may be either symbolic I/O tags or absolute memory references. Confirm the operand type by opening the symbol table or by hovering the address in the LAD/FBD editor.

Decoding UEBW (Ueberwachung)

UEBW is a contraction of Ueberwachung (English: monitoring / supervision / watch-dog). On a block named stoerung (failure/fault), the UEBW input is the monitoring-enable or fault-acknowledgment path that arms the block's fault-detection logic.

In the on-sheet excerpt:

-OFF  --!uebw   stme !-- F173.6
-S36  --!stbe         !
-horn --!zeit         !

the input labelled -OFF- connected to UEBW suggests a global fault-clear or off-condition. When UEBW is true (active), the block evaluates its monitored conditions; when false, the block is held in a benign state. Implementations vary:

• Enable-gate variant: UEBW=TRUE arms the fault logic; UEBW=FALSE latches the last state or forces outputs off.
• Acknowledge variant: a positive edge on UEBW acknowledges the latched fault, resetting STME if the underlying condition has cleared.
• Source-monitor variant: UEBW is wired directly from a sensor that indicates the source of the fault (a contactor, thermal overload, or process value out-of-range signal).

Decoding STBE

STBE is not a single fixed German word. It is a portmanteau almost always parsed as Stoerung Beseitigung (English: fault removal / fault reset) or Stoerung Betaetigung (fault actuation). The exact role depends on the block context. Two practical readings:

1. Reset pushbutton (S36). The on-sheet snippet shows -S36- wired to STBE. S36 is consistent with a hardware input from a pushbutton (German naming: S for Taster/Schalter + index). In that case STBE is the manual fault-cancel / acknowledge input that clears the latched STME output.
2. Fault source. In other stoerung blocks where multiple instances coexist, STBE may instead be the binary input that carries the actual fault bit from the field device (motor overload, end-switch tripped, level high). The block author then uses the same mnemonic for two different meanings.

Resolution rule: trace STBE back to its upstream assignment. If it comes from an input byte/word (e.g., IW 4 or a symbol such as Stoerung_S36), it is a fault source. If it comes from a discrete input terminal symbolised as a button (S36, S_RESET, Taster_Quit), it is a reset.

Decoding STME

STME is parsed as Stoermeldung or Stoerungsmeldung (English: fault message / fault indication). On the stoerung FB it is the output: a latched Boolean flag, conventionally high (true) when the fault condition is active and not yet acknowledged.

The on-sheet excerpt wires STME to F173.6:

• F = Flag (German: Flaggenmerker) — the CPU's process-image-style bit memory area.
• 173 = flag byte address.
• .6 = bit position within that byte (bit 6, zero-indexed in Siemens convention, value = 38).

The same STME bit typically drives three downstream effects in a German Siemens installation:

1. An HMI fault page or WinCC / TIA WinCC message archive entry.
2. An annunciator or horn (often the horn input shown wired to ZEIT on the same block — see below).
3. A group stop or interlock that prevents machine restart until the bit clears.

Decoding ZEIT and the Timer Symbol

ZEIT is the German word for time. On the stoerung block, the ZEIT input activates an internal on-delay timer that delays or filters the fault message — for example, holding STME false until the input has been continuously active for 0.5 s (debounce), or delaying the horn trigger by 1.4 s to avoid spurious alarms.

The timer symbol on the sheet is:

+--------------+
|   ! T!  -   !O!  |
DW 14     --!TV     BI ! --
!      DE ! -- DW114
!         |
+-! RV    Q ! -
+-------------+

Resolving the preset value (0.4 s vs 1.4 s): The block diagram alone is not sufficient to determine whether the timer preset is 0.4 s, 1.4 s, or another value. DW 14 is an indirect reference: the timer reads its preset from data word 14 of the currently opened DB. The actual value depends on:

1. The content of the DB (look up DBW 14 in the DB editor; the value will be in S5TIME format).
2. Any HMI or supervisory system that writes to DBW 14 at runtime.
3. Any initialisation logic in the FB that loads DBW 14 from a constant or another data source.

Use the S5TIME decode rule to read the value directly: in S5TIME the high nibble carries the time base (00 = 10 ms, 01 = 100 ms, 10 = 1 s, 11 = 10 s) and the remaining 12 bits carry the BCD-coded time value.

Example decode (S5TIME in 16-bit word):
  Hex value     : W#16#1294
  High nibble   : 1  -> time base = 100 ms
  Remaining BCD : 294 -> decimal 294
  Preset time   : 294 * 100 ms = 29.4 s

Memory Areas: DW, FW, and F Bits

Classic STEP 7 reserves a flat byte-addressable memory area, portioned by Merker (flags) and accessible as bytes, words, or double words. The German abbreviations on the sheet map as follows:

The ≤ Compare Instruction

The second excerpt shows a comparison block:

+-------+
DW 1  --! ≤   F!
FW 16 --!    Q!----   F163.1
+-------+

This is the German STEP 7 FBD representation of an IEC 61131-3 less-than-or-equal compare. The function block has two inputs and two outputs:

The statement is therefore: "If the value of data word 1 in the currently opened DB is less than or equal to the value of flag word 16, then flag bit M163.1 is set high." The data type (INT, DINT, REAL) is selected when the block is inserted and must match both operands; mismatched types generate compile errors.

Complete FB 205 Example Breakdown

Combining every clue in the on-sheet fragment, FB 205 named stoerung implements a generic fault-handling block:

Functional interpretation: the block monitors a fault condition. UEBW arms the monitoring; STBE acknowledges the latched fault when the operator presses the S36 button; ZEIT drives an on-delay timer that pulses the horn tag after a configurable interval; STME exposes the latched fault status to the rest of the program. Engineers encountering the same block elsewhere in the same project should assume identical semantics unless the symbol table or comments indicate otherwise.

Field Workflow for Decoding Unknown Parameters

Use this sequence when faced with an unfamiliar German-named FB in a STEP 7 project:

1. Open the symbol table. Filter by the block name (stoerung) and the suspected operands to confirm whether they are symbolic or absolute.
2. Open the FB source in STL. Right-click FB 205 in the offline blocks folder and choose Open in STL (or generate source from blocks: Options > Charts > Generate Source).
3. Annotate inputs/outputs. Match the first network of the STL against the FBD on-sheet: U (AND), UN (AND-NOT), O (OR), SV, SE, SS, SA (timer types) reveal the role of each port.
4. Decode timer presets. Read DBW 14 in online mode with the DB open, or interpret the S5TIME BCD code per the rule shown above.
5. Translate comments. Use a translation tool such as Google Translate or Microsoft Translator to convert German block comments, network titles, and symbol descriptions to the working language. For batch conversion of large documentation, the Google Translate Chrome extension or the Google Translate Android app lets you translate on-screen text in place.
6. Cross-reference with cross-reference (REF). In STEP 7, Options > Reference Data > Display shows where each operand is read and written. This resolves whether STBE is an input written from the field or an output driven by the FB.
7. Document the decoded glossary. Add the decoded terms to the project symbol table as symbol comments so that the next engineer inherits a translated legend.

Translation Tool Selection for PLC Documentation

Translation accuracy matters when a single misplaced word changes the safety implication of a logic block. For PLC documentation:

Verification Checklist

After decoding, verify each parameter against the live system:

1. Open the FB in online mode and force UEBW high. STME should reflect the underlying condition after the timer expires.
2. Press the S36 pushbutton physically or via simulation. The latched STME bit should clear if the fault has been removed.
3. Trigger the horn path by driving the horn input high and confirm the on-delay matches DBW 14.
4. Modify DBW 14 online (in RUN with appropriate safety clearance) and observe whether DW 114 (binary time output) reports the expected remaining time.
5. Run the cross-reference to confirm that F163.1 and F173.6 are not driven elsewhere in the program in conflicting ways.
6. Document every translated term and decision in the project folder so the next engineer inherits the decoded glossary.

Troubleshooting Matrix

FAQ