Statement List (STL) - DCE FEL ČVUT v Praze

6 Logic Control Instructions
6.1 Overview of Logic Control Instructions
Description
You can use the Jump instructions to control the flow of logic, enabling your program
to interrupt its linear flow to resume scanning at a different point. You can use the
LOOP instruction to call a program segment multiple times.
The address of a Jump or Loop instruction is a label. A jump label may be as many
as four characters, and the first character must be a letter. Jumps labels are followed
with a mandatory colon ":" and must precede the program statement in a line.
Note
Please note for S7– 300 CPU programs that the jump destination always (not for
318– 2) forms the beginning of a Boolean logic string in the case of jump
instructions. The jump destination must not be included in the logic string.
You can use the following jump instructions to interrupt the normal flow of your
program unconditionally:
• JU Jump Unconditional
• JL Jump to Labels
The following jump instructions interrupt the flow of logic in your program based on
the result of logic operation (RLO) produced by the previous instruction statement:
• JC Jump if RLO = 1
• JCN Jump if RLO = 0
• JCB Jump if RLO = 1 with BR
• JNB Jump if RLO = 0 with BR
The following jump instructions interrupt the flow of logic in your program based on
the signal state of a bit in the status word:
• JBI Jump if BR = 1
• JNBI Jump if BR = 0
• JO Jump if OV = 1
• JOS Jump if OS = 1
Statement List (STL) for S7-300 and S7-400 Programming
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