Siemens Awl Stl Programmer

Siemens S7 STL (AWL) Programming Skill

Overview

Generate Siemens S7-300 / S7-400 / S7-1500 Statement List (STL / AWL) programs compatible with Step7 Classic and TIA Portal.

Core model knowledge:

• Accumulator-based execution (ACCU1 / ACCU2)
• RLO (Result of Logic Operation) for boolean logic
• S5 timers, IEC timers (TON/TOF/TP), counters, INT and REAL arithmetic
• OB / FB / FC / DB block hierarchy
• Standard scan cycle model (Read → Execute → Write)

For full instruction syntax, see references/STL_Core_Instructions.md.

Critical Rule: Omit Block Number (NAME) Line

Always omit the NAME : '<number>' line unless the user specifically requests a fixed block number. TIA Portal automatically assigns the next available unused block number on import.

Block Structure

Organization Block (OB)

ORGANIZATION_BLOCK "OB1"
TITLE = Main Program Cycle
{ S7_Optimized_Access := 'TRUE' }
VERSION : 0.1

VAR_TEMP
      TempVar : Int;
END_VAR

BEGIN
NETWORK
TITLE = Example Network
      L     PIW256;
      T     #TempVar;
END_ORGANIZATION_BLOCK

Function (FC) — Stateless

FUNCTION "FC_Name" : Void
{ S7_Optimized_Access := 'TRUE' }
VERSION : 0.1

VAR_INPUT
    IN : Int;
END_VAR

VAR_OUTPUT
    OUT : Real;
END_VAR

BEGIN
NETWORK
TITLE = Convert and Scale
      L     #IN;
      ITD;
      DTR;
      T     #OUT;
END_FUNCTION

Function Block (FB) — Stateful

FUNCTION_BLOCK "FB_Name"
{ S7_Optimized_Access := 'TRUE' }
VERSION : 0.1

VAR_INPUT
    StartPB : BOOL;
    StopPB  : BOOL;
END_VAR

VAR_OUTPUT
    MotorOut : BOOL;
END_VAR

VAR
    RunLatch : BOOL;
    Delay    : TON;
END_VAR

BEGIN
NETWORK
TITLE = Start Latch
      A     #StartPB;
      AN    #StopPB;
      S     #RunLatch;

NETWORK
TITLE = Output
      A     #RunLatch;
      =     #MotorOut;
END_FUNCTION_BLOCK

Data Block (DB)

DATA_BLOCK "DB_Name"
{ S7_Optimized_Access := 'TRUE' }
VERSION : 0.1
NON_RETAIN

VAR
    Value : Int;
END_VAR

BEGIN
END_DATA_BLOCK

Key Formatting Rules

• Always include { S7_Optimized_Access := 'TRUE' } after block keyword
• Use symbolic quoted names ("BlockName") — never numeric references
• Prefix local variables with # (e.g., #StartPB)
• Each instruction ends with ;
• Use NETWORK + TITLE = ... + // comment for each logical group

Timer Selection:

• Inside FC: Use S5 timers (SE, SP, SD, SA, SS)
• Inside FB: Use IEC timers (TON, TOF, TP)

Code Generation Constraints

MUST:

• Use symbolic quoted names for all block references
• Generate complete, compilable blocks
• Separate logical groups into individual NETWORKs
• Use uppercase STL mnemonics (A, AN, O, =, S, R, L, T, FP, ITD, DTR, etc.)
• Generate matching instance DB when generating an FB

MUST NOT:

• Mix LAD, SCL, or non-STL syntax
• Use numeric-only block references unless user explicitly requests
• Include NAME : '<number>' in generated blocks

When to Consult Documentation

If the user's request involves instructions or patterns not covered here, consult:

• TIA Portal STL Reference: https://docs.tia.siemens.cloud/r/en-us/v21/creating-stl-programs-s7-300-s7-400-s7-1500
• Full instruction reference: references/STL_Core_Instructions.md
• Block templates: references/REFERENCE.md
• Formatting rules: references/FORMATTING.md

Typical cases requiring documentation lookup:

• Interrupt OBs (OB35, OB40, OB80) and their startup VAR_TEMP
• System function calls (SFC, SFB) such as CALL SFC14
• String handling, DATE_AND_TIME types
• BLKMOV, FILL, UBLKMOV block move instructions
• Less common accumulator operations (CAD, CAW, TAK, PUSH, POP)