Scl Overview; Scl Program Editor - Siemens SIMATIC S7-1200 Manual

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6.2 Easy-to-use programming languages
6.2.3

SCL overview

Structured Control Language (SCL) is a high-level, PASCAL-based programming language
for the SIMATIC S7 CPUs. SCL supports the block structure of STEP 7. You can also
include program blocks written in SCL with program blocks written in LAD and FBD.
SCL instructions use standard programming operators, such as for assignment (:=),
mathematical functions (+ for addition, - for subtraction, * for multiplication, and / for division).
SCL uses standard PASCAL program control operations, such as IF-THEN-ELSE, CASE,
REPEAT-UNTIL, GOTO and RETURN. You can use any PASCAL reference for syntactical
elements of the SCL programming language. Many of the other instructions for SCL, such as
timers and counters, match the LAD and FBD instructions.
Because SCL, like PASCAL, offers conditional processing, looping, and nesting control
structures, you can implement complex algorithms in SCL more easily than in LAD or FBD.
The following examples show different expressions for different uses:
"C" := #A+#B;
"Data_block_1".Tag := #A;
IF #A > #B THEN "C" := #A;
"C" := SQRT (SQR (#A) + SQR (#B));
As a high-level programming language, SCL uses standard statements for basic tasks:
● Assignment statement: :=
● Mathematical functions: +, -, *, and /
● Addressing of global variables (tags): "<tag name>" (Tag name or data block name
enclosed in double quotes)
● Addressing of local variables: #<variable name> (Variable name preceded by "#" symbol)
● Absolute addressing: %<absolute address>, for example %I0.0 or %MW10
Arithmetic operators can process various numeric data types. The data type of the result is
determined by the data type of the most-significant operands. For example, a multiplication
operation that uses an INT operand and a REAL operand yields a REAL value for the result.
6.2.4

SCL program editor

You can designate any type of block (OB, FB, or FC) to use the SCL programming language
at the time you create the block. STEP 7 provides an SCL program editor that includes the
following elements:
● Interface section for defining the parameters of the code block
● Code section for the program code
● Instruction tree that contains the SCL instructions supported by the CPU
You enter the SCL code for your instruction directly in the code section. The editor includes
buttons for common code constructs and comments. For more complex instructions, simply
drag the SCL instructions from the instruction tree and drop them into your program. You can
also use any text editor to create an SCL program and then import that file into STEP 7.
96
Assigns two local variables to a tag
Assignment to a data block tag
Condition for the IF-THEN statement
Parameters for the SQRT instruction
Manual, 03/2014, A5E02486774-AF
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