IEC 61131-3 is the third part of the open international standard IEC 61131, and was first published in December 1993 by the IEC. The current (second) edition was published in 2003.
Part 3 of IEC 61131 deals with programming languages and defines two graphical and two textual PLC programming language standards:
- Ladder diagram (LD), graphical
- Function block diagram (FBD), graphical
- Structured text (ST), textual
- Instruction list (IL), textual
- Sequential function chart (SFC), has elements to organize programs for sequential and parallel control processing.
Contents |
Data Types
- Bit Strings - groups of on/off values
- INTEGER - whole numbers
- SINT - signed short (1 byte)
- INT - signed integer (2 byte)
- DINT - double integer (4 byte)
- LINT - long integer (8 byte)
- U - Unsigned - add a U to the type to make it unsigned integer.
- REAL - floating point IEC 559 (IEEE)
- REAL - (4 byte)
- LREAL - (8 byte)
- Time - duration for timers, processes.
- Date and Time of day:
- DATE - calendar date
- TIME_OF_DAY - clock time
- DATE_AND_TIME: time and date
- STRING - character strings surrounded by single quotes.
Escaped characters are preceded by a dollar sign.
($$ $' $L $N $P $R $T $xx) => ($ quote linefeed newline page(FF) return tab hex_value)- WSTRING - holds multi-byte strings.
- Arrays - multiple values stored in the same variable.
- Sub Ranges - puts limits on value i.e., (4-20) for current
- Derived - type derived from one of the above types.
- TYPE - single type
- STRUCT - composite of several variables and types.
- Generic - groups of the above types:
- ANY
- ANY_DERIVED
- ANY_ELEMENTARY
- ANY_MAGNITUDE
- ANY_NUM - LREAL, REAL
- ANY_INT - LINT, DINT, INT, SINT, ULINT, UDINT, UINT, USINT
- ANY_BIT - LWORD, DWORD, WORD, BYTE, BOOL
- ANY_STRING - STRING, WSTRING
- ANY_DATE - DATE, TOD, DT
- ANY
Variables
Variable attributes: RETAIN, CONSTANT, AT
- Global
- Direct (local)
- I/O Mapping - Input, Output, I/O
- External
- Temporary
Configuration
- Resource - Like a CPU
- Tasks - Can be multiple per CPU.
- Programs - Can be executed once, on a timer, on an event.
Program Organization Units
- Functions
- Standard: ADD, SQRT, SIN, COS, GT, MIN, MAX, AND, OR, etc.
- Custom
- Function Blocks
- Standard:
- Custom - Libraries of functions can be supplied by a vendor or third party.
- Programs
Configuration, Resources, Tasks
- Configuration - processing resources, memory for IO, execution rates, number of tasks.
External links
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