Jumps - Omron SYSMAC C20P Operation Manual

The Ladder Diagram
IL(02)
0000
0003
4–3–5

Jumps

It's interesting to notice that if any instructions are added to an interlocked
section of a diagram, they in essence branch from the branching point where
the Interlock instruction is located, regardless of whether they are drawn that
way or whether they are drawn connected directly to the bus bar. If we add a
third instruction between instruction 2 and the Interlock Clear instruction to
diagram B from above, we can connected it either as another branch line fol-
lowing the branch line for instruction 2 or directly to the bus bar. In either
case, the diagram, when rewritten into the type of display shown above for
GPC displays, would be the same. Both diagrams would naturally execute
exactly the same.
0001
Instruction 1
0002
Instruction 2
Instruction 3
ILC(03)
0000
0001
0002
0003
When drawing interlocked sections of ladder diagrams, either form may be
used. The non-branching form will be used in the remainder of this manual.
A specific section of a program can be skipped according a designated exe-
cution condition. Although this is similar to what happens when the execution
condition for an Interlock instruction is OFF, with jumps, the operands for all
instructions maintain status. Jumps can therefore be used to control devices
that require a sustained output, e.g., pneumatics and hydraulics, whereas
interlocks can be used to control devices that do not required a sustained
output, e.g., electronic instruments.
Jumps are created using the Jump (JMP(04)) and Jump End (JME(05)) in-
structions. If the execution condition for a Jump instruction is ON, the pro-
gram is executed normally as if the jump did not exist. If the execution condi-
tion for the Jump instruction is OFF, program execution moves immediately
to a Jump End instruction without changing the status of anything between
the Jump and Jump End instruction.
In the following example, Instructions 1 and 2 would not be executed when
IR 0000 is OFF and execution would skip immediately to the Jump End in-
struction without change the status of any bits or words in between. If IR
0000 is ON, the program would be executed as if the jump did not exist.
IL(02)
0000 0001
0002
0003
IL(02)
Instruction 1
Instruction 2
Instruction 3
ILC(03)
Section 4–3
Instruction 1
Instruction 2
Instruction 3
ILC(03)
39