Jump Operations - Siemens SIMATIC S5 Manual

S5-115F Manual
3.2.10 Dump Operations
Table 3-20 provides an overview of the jump operations. An example follows the table.
Operation Operand
JU =
JC =
JZ =
JN =
JP =
JM =
JO =
ID
Jump label
(up to 4)
Processing the jump operations
A symbolic jump destination (jump label) must always be entered next to a jump operation. This
jump label can have up to four characters, the first of which must be a letter of the alphabet.
When programming, please be aware of the following:
• The absolute jump displacement cannot exceed + 127 or - 128 words in the program memory.
Some statements take up two words (e.g. "Load a constant"). For long jumps, insert an
intermediate destination.
• Jumps can be executed only within a block.
• Jumping over segment boundaries ("BLD 255") is not permitted, i.e. jumps to networks are
illegal.
• Jumps from expressions in parentheses are not permitted.
EWA 4NEB 811 6149-02
Table 3-20. Overview of Jump Operations
Jump unconditionally.
The unconditional jump is executed independently of conditions.
Jump conditionally.
The conditional jump is executed if the RLO is "1". If the RLO is
"0", the statement is not executed and the RLO is set to "1".
Jump if the result is "zero".
The jump is executed only if CC 1 = 0 and CC 0 = 0.
The RLO is not changed.
Jump if the result is "not zero".
The jump is executed only if CC 1 CC 0.
The RLO is not changed.
Jump if the result is positive.
The jump is executed only if CC 1 = 1 and CC 0 = 0.
The RLO is not changed.
Jump if the result is negative.
The jump is executed only if CC 1 = 0 and CC 0 = 1.
The RLO is not changed.
Jump on overflow.
The jump is executed if an overflow occurs. Otherwise the jump is
not executed. The RLO is not changed.
Meaning
STEP 5 Operations
3-57