NEMA IA 2.3:2005

FOREWORD
1 General
  1.1 Scope
  1.2 Normative references
  1.3 Definitions
  1.4 Overview and general requirements
      1.4.1 Software model
      1.4.2 Communication model
      1.4.3 Programming model
  1.5 Compliance
      1.5.1 System compliance
      1.5.2 Program compliance
2 Common elements
  2.1 Use of printed characters
      2.1.1 Character set
      2.1.2 Identifiers
      2.1.3 Keywords
      2.1.4 Use of white space
      2.1.5 Comments
      2.1.6 Pragmas
  2.2 External representation of data
      2.2.1 Numeric literals
      2.2.2 Character string literals
      2.2.3 Time literals
  2.3 Data types
      2.3.1 Elementary data types
      2.3.2 Generic data types
      2.3.3 Derived data types
  2.4 Variables
      2.4.1 Representation
      2.4.2 Initialization
      2.4.3 Declaration
  2.5 Program organization units
      2.5.1 Functions
      2.5.2 Function blocks
      2.5.3 Programs
  2.6 Sequential Function Chart (SFC) elements
      2.6.1 General
      2.6.2 Steps
      2.6.3 Transitions
      2.6.4 Actions
      2.6.5 Rules of evolution
      2.6.6 Compatibility of SFC elements
      2.6.7 SFC Compliance requirements
  2.7 Configuration elements
      2.7.1 Configurations, resources, and access paths
      2.7.2 Tasks
3 Textual languages
  3.1 Common elements
  3.2 Instruction list (IL)
      3.2.1 Instructions
      3.2.2 Operators, modifiers and operands
      3.2.3 Functions and function blocks
  3.3 Structured Text (ST)
      3.3.1 Expressions
      3.3.2 Statements
4 Graphic languages
  4.1 Common elements
      4.1.1 Representation of lines and blocks
      4.1.2 Direction of flow in networks
      4.1.3 Evaluation of networks
      4.1.4 Execution control elements
  4.2 Ladder diagram (LD)
      4.2.1 Power rails
      4.2.2 Link elements and states
      4.2.3 Contacts
      4.2.4 Coils
      4.2.5 Functions and function blocks
      4.2.6 Order of network evaluation
  4.3 Function Block Diagram (FBD)
      4.3.1 General
      4.3.2 Combination of elements
      4.3.3 Order of network evaluation
ANNEX A (normative) Specification method for textual languages
  A.1 Syntax
       A.1.1 Terminal symbols
       A.1.2 Non-terminal symbols
       A.1.3 Production rules
  A.2 Semantics
ANNEX B (normative) Formal specifications of language elements
  B.0 Programming model
  B.1 Common elements
       B.1.1 Letters, digits and identifiers
       B.1.2 Constants
       B.1.3 Data types
       B.1.4 Variables
       B.1.5 Program organization units
       B.1.6 Sequential function chart elements
       B.1.7 Configuration elements
  B.2 Language IL (Instruction List)
       B.2.1 Instructions and operands
       B.2.2 Operators
  B.3 Language ST (Structured Text)
       B.3.1 Expressions
       B.3.2 Statements
ANNEX C (normative) Delimiters and keywords
ANNEX D (normative) Implementation-dependent parameters
ANNEX E (normative) Error conditions
ANNEX F (informative) Examples
  F.1 Function WEIGH
  F.2 Function block CMD_MONITOR
  F.3 Function block FWD_REV_MON
  F.4 Function block STACK_INT
  F.5 Function block MIX_2_BRIX
  F.6 Analog signal processing
       F.6.1 Function block LAG1
       F.6.2 Function block DELAY
       F.6.3 Function block AVERAGE
       F.6.4 Function block INTEGRAL
       F.6.5 Function block DERIVATIVE
       F.6.6 Function block HYSTERESIS
       F.6.7 Function block LIMITS_ALARM
       F.6.8 Structure ANALOG_LIMITS
       F.6.9 Function block ANALOG_MONITOR
       F.6.10 Function block PID
       F.6.11 Function block DIFFEQ
       F.6.12 Function block RAMP
       F.6.13 Function block TRANSFER
  F.7 Program GRAVEL
  F.8 Program AGV
  F.9 Use of enumerated data types
  F.10 Function block RTC (Real Time Clock)
  F.11 Function block ALRM_INT
ANNEX G (informative) Reference character set
Index

Specifies syntax and semantics of programming languages for PLC as defined in Part 1 of IEC 61131.