PLC concepts
5.4 Data types
S7-1200 Programmable controller
System Manual, V4.2, 09/2016, A5E02486680-AK
125
Data types are used to specify both the size of a data element as well as how the data are to
be interpreted. Each instruction parameter supports at least one data type, and some
parameters support multiple data types. Hold the cursor over the parameter field of an
instruction to see which data types are supported for a given parameter.
A formal parameter is the identifier on an instruction that marks the location of data to be
used by that instruction (example: the IN1 input of an ADD instruction). An actual parameter
is the memory location (preceded by a "%" character) or constant containing the data to be
used by the instruction (example %MD400 "Number_of_Widgets"). The data type of the
actual parameter specified by you must match one of the supported data types of the formal
parameter specified by the instruction.
When specifying an actual parameter, you must specify either a tag (symbol) or an absolute
(direct) memory address. Tags associate a symbolic name (tag name) with a data type,
memory area, memory offset, and comment, and can be created either in the PLC tags
editor or in the Interface editor for a block (OB, FC, FB and DB). If you enter an absolute
address that has no associated tag, you must use an appropriate size that matches a
supported data type, and a default tag will be created upon entry.
All data types except String, Struct, Array, and DTL are available in the PLC tags editor and
the block Interface editors. String, Struct, Array, and DTL are available only in the block
Interface editors. You can also enter a constant value for many of the input parameters.
● Bit and Bit sequences (Page 126): Bool (Boolean or bit value), Byte (8-bit byte value),
Word (16-bit value), DWord (32-bit double word value)
● Integer (Page 127)
– USInt (unsigned 8-bit integer), SInt (signed 8-bit integer),
– UInt (unsigned 16-bit integer), Int (signed 16-bit integer)
– UDInt (unsigned 32-bit integer), DInt (signed 32-bit integer)
● Floating-point Real (Page 127): Real (32-bit Real or floating-point value), LReal (64-bit
Real or floating-point value)
● Time and Date (Page 128): Time (32-bit IEC time value), Date (16-bit date value), TOD
(32-bit time-of-day value), DTL (12-byte date-and-time structure)
● Character and String (Page 130): Char (8-bit single character), String (variable-length
string of up to 254 characters)
● Array (Page 132)
● Data structure (Page 133): Struct
● PLC data type (Page 133)
● Variant data type (Page 134)
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