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Drum, Shift & Search

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

Shift register

shift(C.select(1, 8)) \
    .clock(ClockBit) \
    .reset(ResetBit)
  • Rung condition is the data bit inserted at position 1
  • Clock — shift occurs on the rising edge of the clock condition
  • Reset — level-sensitive: clears all bits in range while True
  • Terminal after .clock(...).reset(...).

Direction is determined by the range order: - C.select(1, 8) → shifts low-to-high (data enters at C1, exits at C8) - C.select(1, 8).reverse() → shifts high-to-low

Event drum

with Rung(Running):
    event_drum(
        outputs=[DrumOut1, DrumOut2, DrumOut3],
        events=[DrumEvt1, DrumEvt2, DrumEvt3, DrumEvt4],
        pattern=[
            [1, 0, 0],
            [0, 1, 0],
            [0, 0, 1],
            [1, 1, 0],
        ],
        current_step=DrumStep,
        completion_flag=DrumDone,
    ) \
        .reset(ShiftReset) \
        .jump((AutoMode, Found), step=DrumJumpStep) \
        .jog(Clock, Found)

Time drum

with Rung(Running):
    time_drum(
        outputs=[DrumOut1, DrumOut2, DrumOut3],
        presets=[50, DS[1], 75, DS[2]],
        unit="ms",
        pattern=[
            [1, 0, 0],
            [0, 1, 0],
            [0, 0, 1],
            [1, 1, 0],
        ],
        current_step=DrumStep,
        accumulator=DrumAcc,
        completion_flag=DrumDone,
    ) \
        .reset(ShiftReset) \
        .jump(Found, step=2) \
        .jog(Start)

event_drum(...) and time_drum(...) are terminal builders. .reset(...) is required and finalizes the instruction. .jump(...) and .jog(...) are optional.

Variadic condition chaining

Builder condition arguments (.down(...), .clock(...), .reset(...), .jump(...), .jog(...)) all accept single conditions, multiple positional conditions, or tuple/list groups. All forms normalize to one AND expression:

event_drum(...).reset(ResetA, ResetB).jog(JogA, JogB)
event_drum(...).jump((AutoMode, Found), step=2)

Find the first element in a range matching a condition:

search(
    DS.select(1, 100) >= 100,
    result=FoundAddr,
    found=FoundFlag,
)

The first argument is a comparison expression built from a .select() range — the same operator syntax tags use elsewhere in the DSL.

  • On success: result = matched_address (1-based), found = True
  • On miss: result = -1, found = False
  • result must be INT or DINT; found must be BOOL

Continuous search (resume from last position)

search(
    DS.select(1, 100) >= 100,
    result=FoundAddr, found=FoundFlag,
    continuous=True,
)
  • result == 0 → restart at first address
  • result == -1 → already exhausted; return miss without rescanning
  • otherwise → resume at first address after current result

Text search

search(
    Txt.select(1, 50) == "AB",     # Search for substring "AB"
    result=FoundAddr, found=FoundFlag,
)

Only == and != are valid for CHAR ranges. Matches windowed substrings of length equal to the value string.