Elementary Data Types

Introduction

Fernhill SCADA supports these elementary data types:

Keyword	Description	Range
BOOL	Boolean value	0 or 1
SINT	Short integer	-128 to +127
USINT	Unsigned short integer	0 to 255
BYTE	Single byte bitmask	16#00 to 16#FF
INT	Integer	-32768 to +32767
UINT	Unsigned integer	0 to 65535
WORD	Two byte bitmask	16#0000 to 16#FFFF
DINT	Double integer	-2147483648 to +2147483647
UDINT	Unsigned double integer	0 to 4294967295
DWORD	Four byte bitmask	16#00000000 to 16#FFFFFFFF
LINT	Long integer	-9223372036854775808 to +9223372036854775807
ULINT	Unsigned long integer	0 to 18446744073709551615
LWORD	Eight byte bitmask	16#0000000000000000 to 16#FFFFFFFFFFFFFFFF
REAL	Single precision floating point	-
LREAL	Double precision floating point	-
TIME	Interval value	-
DATE	Date value	1601-01-01 to 9999-12-31
TIME_OF_DAY or TOD	Time of day	00:00:00.000 to 23:59:59.999
DATE_AND_TIME or DT	Date and time value	1601-01-01-00:00:00.000 to 9999-12-31-23:59:59.999
CHAR	Single byte character	$00 to $FF
WCHAR	Double byte character	$0000 to $FFFF
STRING	Variable length single byte character string	-
WSTRING	Variable length double byte character string	-

STRING and WSTRING Types

The STRING and WSTRING types store a variable number of characters up to a maximum limit.

STRING and WSTRING types can be declared with or without a size parameter. For example:

VAR
    (* No size parameter, maximum length is 254 characters *)
    Notes : STRING;

    (* The size parameter sets the length to 4096 characters *)
    SQLCommand : STRING[4096];  
END_VAR

The maximum length of the STRING and WSTRING types declared without a size parameter is 254 characters.

The size parameter of a string must be in the range 1 to 65535.

Accessing Characters of a STRING or WSTRING

Use the array index operator [] to access a character of a string type. The index in the array operator starts at position 1. For example:

VAR
    State : STRING[16] := 'Stopped';
    Ch : CHAR;
END_VAR

    Ch := State[1];     (* Assigns 'S' to Ch *)
    Ch := State[7];     (* Assigns 'd' to Ch *)

Automatic Type Promotion

Elementary Types have a priority defined by the position in the above table. For example type REAL is higher priority than type INT.

When two different types are used in an operation automatic type promotion occurs. The inputs to the operation are all promoted to the same type as the highest priority input. For example if an INT is added to a REAL, the INT value is promoted to a REAL before the addition operation. The return value from this operation will be REAL.

Standards Compliance

IEC 61131-3 Second Edition: Table 10.

IEC 61131-3 Third Edition: Table 10.

Further Information

Numeric Literals

To learn about literals to represent numeric values.

Character String Literals

To learn about literals to represent characters and strings.

Date and Time of Day Literals

To learn about literals to represent dates and time of day.

Time Literals

To learn about literals to represent a time interval.

Common Elements

To learn about other language Common Elements.

Glossary

For the meaning of terms used in Fernhill SCADA.