IEC61131 Common Elements

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IEC 61131-3 is a standard in computer programming languages. The five languages to which this standard applies share common elements so different languages can be used in the same program.

1 Data Types
2 Variables
3 Configuration
4 Program Organization Units
5 Configuration, Resources, Tasks

[edit] Data Types

Bit Strings - groups of on/off values
- BOOL - 1
- BYTE - 8
- WORD - 16
- DWORD - 32
- LWORD - 64

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, UNIT, USINT
  - ANY_BIT - LWORD, DWORD, WORD, BYTE, BOOL
  - ANY_STRING - STRING, WSTRING
  - ANY_DATE - DATE, TOD, DT

[edit] Variables

Variable attributes: RETAIN, CONSTANT, AT

Global
Direct (local)
I/O Mapping - Input, Output, I/O
External
Temporary

[edit] Configuration

Resource - Like a CPU
Tasks - Can be multiple per CPU.
Programs - Can be executed once, on a timer, on an event.

[edit] 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