Statement List (STL) - DCE FEL ČVUT v Praze

Logic Control Instructions
6.15 JM Jump if Minus
Format
Description
Status word
Example
JM
Address Description
Symbolic name of jump destination.
If status bits CC 1 = 0 and CC 0 = 1, JM (jump if result < 0) interrupts
the linear program scan and jumps to a jump destination. The linear program scan
resumes at the jump destination. The jump destination is specified by a jump label.
Both forward and backward jumps are possible. Jumps may be executed only within
a block, that is, the jump instruction and the jump destination must lie within one and
the same block. The jump destination must be unique within this block. The
maximum jump distance is -32768 or +32767 words of program code. The actual
maximum number of statements you can jump over depends on the mix of the
statements used in your program (one-, two-, or three word statements).
BR CC 1 CC 0 OV OS OR STA RLO /FC
writes: - - - - - - - - -
STL Explanation
L IW8
L MW12
-I //Subtract contents of MW12 from contents of IW8.
JM NEG //Jump if result < 0 (that is, contents of ACCU 1 < 0).
AN M 4.0 //Program scan continues here if jump is not executed.
S M 4.0
JU NEXT
NEG: AN M 4.1 //Program scan resumes here after jump to jump label NEG.
S M 4.1
NEXT: NOP 0 //Program scan resumes here after jump to jump label NEXT.
Statement List (STL) for S7-300 and S7-400 Programming
6-16 A5E00706960-01