Program Control

For an introduction to the DSL vocabulary, see Core Concepts.

Programs

Two equivalent ways to define a program:

# Context manager
with Program() as logic:
    with Rung(Start):
        latch(Running)

# Decorator
@program
def logic():
    with Rung(Start):
        latch(Running)

Both produce a Program you pass to PLC. See Core Concepts — Programs for details.

Subroutines

Context-manager style

with Program() as logic:
    with subroutine("startup"):
        with Rung(Step == 0):
            out(InitLight)

    with Rung(AutoMode):
        call("startup")

Decorator style

@subroutine("init")
def init_sequence():
    with Rung():
        out(InitLight)

with Program() as logic:
    with Rung(Button):
        call(init_sequence)     # auto-registers and calls

For loops

forloop repeats a block of instructions N times within a single scan:

with Rung():
    with forloop(5):
        copy(Counter + 1, Counter)

The count can be a literal or a tag (resolved each scan):

with Rung():
    with forloop(LoopCount):
        copy(Counter + 1, Counter)

Use loop.idx for indirect addressing inside the loop body:

with Rung():
    with forloop(3) as loop:
        copy(Src[loop.idx + 1], Dst[loop.idx + 1])

End and return instructions aren't needed — Python indentation handles scope.