🚧 Change module numbering

plugins/pump_plant.example.py

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+"""Example plant/PLC model plugin for the pump-station FAT scenario.
+
+In a real FAT bench the PLC under test drives the outputs. For a
+headless demo (or pre-FAT scenario smoke tests) this plugin emulates
+the expected PLC behavior so the scenario can PASS end-to-end.
+
+Register it in a scenario via:
+
+    plugins: [plugins.pump_plant.pump_plant]
+
+The engine calls it once per tick.
+"""
+
+from __future__ import annotations
+
+# latch state per engine instance (module-level dict keyed by id)
+_LATCH = {}
+
+
+def pump_plant(engine, value) -> None:
+    """Emulated PLC with classic start/stop latch circuit:
+
+    - rising edge on start_button latches the pump ON
+    - e-stop OFF breaks the latch (and the safe state follows)
+    - valve follows the pump; speed setpoint follows level above 4000
+    """
+    key = id(engine)
+    start = bool(engine.alias_value("start_button"))
+    em_stop = bool(engine.alias_value("em_stop_ok"))
+    level = float(engine.alias_value("level_sensor"))
+
+    # rising edge of the start button sets the latch; e-stop clears it
+    if engine.consume_rising_edge("start_button"):
+        _LATCH[key] = True
+    if not em_stop:
+        _LATCH[key] = False
+
+    pump_on = _LATCH.get(key, False) and em_stop
+    speed = int(max(0.0, (level - 4000.0) * 10.0)) if pump_on else 0
+
+    _set_do(engine, "pump_relay", pump_on)
+    _set_do(engine, "valve_open", pump_on)
+    _set_ao(engine, "speed_setpoint", speed)
+
+
+def _set_do(engine, alias_name: str, value: bool) -> None:
+    """Emulate a Modbus master writing the output coil.
+
+    Uses the engine's global alias location: ``loc.bit`` is the 0-based
+    global digital channel index == the Modbus bit address (Table 122).
+    """
+    loc = engine.alias_location(alias_name)
+    result = engine.datastore.write_bits(loc.bit, [bool(value)])
+    assert not isinstance(result, Exception), result
+
+
+def _set_ao(engine, alias_name: str, value: int) -> None:
+    """Emulate a Modbus master writing the output register.
+
+    ``loc.word`` is the global analog output word index == the Modbus
+    word address in output area 1 (0x0000-0x00FF).
+    """
+    alias = engine._aliases[alias_name]
+    loc = engine.alias_location(alias_name)
+    raw = int(value * alias.scale + alias.offset) & 0xFFFF
+    result = engine.datastore.write_words(loc.word, [raw])
+    assert not isinstance(result, Exception), result