====== Switcher Block (v3.2) ======

{{:cs:mervis-ide:35-help:switcherblock_v2.0.png}}

===== Description =====
  * **Full function block name:** Lib.Mervis.v3_2.SwitcherBlock
  * **Inherits from:** [[en:mervis-ide:35-help:035-software_basic:060-libraries:060-lib-mervis:015-utilities:040-base-function-blocks:010-basealarmblock:v2_0|Lib.Mervis.v2_0.BaseAlarmBlock]]
  * **Required project references:** Lib.Mervis, Lib.Mervis.Alarms

A universal block for safely switching a single-stage physical device (pump, fan, compressor, valve, heating rod). It bundles the standard functionality needed around such a device: Auto / Manual-On / Manual-Off operating modes, running-feedback supervision, two built-in alarms (Fail-to-start and Failure/Emergency), a periodic exercise "kick", a run-down overrun, an emergency shutdown that overrides everything, and maintenance counters (operating hours and start count). Because it inherits from ''BaseAlarmBlock'', the block exposes a unified alarm interface that can be chained into the project alarm system.

===== ST call =====

<code pascal>
PROGRAM PUMP_CONTROL_DEMO
    VAR
        Heating_Demand  : BOOL;
        Pressure_Switch : BOOL;
        Thermal_Fault   : BOOL;

        PumpSwitcher : Lib.Mervis.v3_2.SwitcherBlock;
        Pump_Relay   : BOOL;
    END_VAR

    PumpSwitcher(
        OperatingMode   := OperatingModeType#Automatic,
        Demand          := Heating_Demand,
        Feedback        := BOOL_TO_USINT(Pressure_Switch), // 0/1; use 2 to ignore feedback
        Failure         := Thermal_Fault,
        RunDown         := T#2m,    // 2 min overrun to dissipate residual heat
        FeedbackTimeout := T#10s    // wait 10 s for pressure to build up
    );

    Pump_Relay := PumpSwitcher.Command;
END_PROGRAM
</code>

===== Inputs =====

^ Name ^ Data Type ^ Allowed Range ^ Retain ^ Required ^ Description ^
| OperatingMode | [[en:mervis-ide:35-help:035-software_basic:060-libraries:060-lib-mervis:015-utilities:030-types:operatingmodetype|OperatingModeType]] | | Yes | No | Desired operating mode (Automatic / On / Off). The "Off" mode is dominant and prevents starting by any other function. Default: ''Off''. |
| Demand | bool | | No | Yes | Request for an operational state in Automatic mode (industry-standard "call for heat / call for run"). Ignored in Manual modes. |
| Feedback | usint | 0..2 | No | No | Running-status feedback. A boolean signal can be mapped directly via ''BOOL_TO_USINT''. Default: ''2'' (feedback not connected → feedback logic is bypassed). |
| FeedbackManual | bool | | No | No | Indicates a manual hardware override (e.g. a HOA switch on the cabinet). Reflected in ''CompositeState''. Default: ''false''. |
| Failure | bool | | No | No | External hardware fault report (motor trip, thermal overload, inverter fault, …). Raises the **Failure** alarm. Default: ''false''. |
| EmergencyShutdown | bool | | No | No | Emergency stop. Immediately deactivates ''Command'' and overrides all modes. Default: ''false''. |
| OperatingHoursReset | bool | | No | No | Rising trigger that resets the operating-hours and start counters. Default: ''false''. |
| ControlFlags | uint | 0..15 | No | No | Bit array defining extended behaviour (see table below). Default: ''0''. |
| RunDown | time | | No | No | Overrun / post-run time: the device keeps running this long after ''Demand'' is removed (heat-dissipation cycles). If ''0'', disabled. Default: ''T#5m''. |
| FeedbackTimeout | time | | No | No | Time allowed for ''Feedback'' to become active after ''Command'' is issued before the **Not Run** alarm is raised. Default: ''T#30s''. |
| KickFunctionInterval | time | | No | No | Interval of the periodic exercise (anti-seize) function. If ''0'', disabled. Default: ''T#0s'' (off). |
| KickFunctionDuration | time | | No | No | How long the device runs during a periodic exercise kick. Default: ''T#1m''. |
| NotRunAlarmPriority | [[en:mervis-ide:35-help:035-software_basic:060-libraries:060-lib-mervis:015-utilities:030-types:alarmprioritytype|AlarmPriorityType]] | | No | No | Alarm class for the "Fail to Start" (Not Running) alarm. Default: ''32''. |
| FailureAlarmPriority | AlarmPriorityType | | No | No | Alarm class for the external Failure alarm. Default: ''32''. |
| EmergencyAlarmPriority | AlarmPriorityType | | No | No | Alarm class for the Emergency-Shutdown-as-alarm reaction (see ControlFlags bit 3). Default: ''32''. |

**Description of Feedback values**
^ Value ^ Meaning ^
| 0 | Feedback inactive (device not running). |
| 1 | Feedback active (device running). |
| 2 | Feedback not connected (default) — feedback logic is bypassed; the running state mirrors ''Command''. |

**Description of ControlFlags values**
^ Bit ^ Mask ^ Meaning ^
| 0 | 1 | If TRUE, all alarm evaluation is completely disabled. |
| 1 | 2 | If TRUE, ''Command'' is dropped on an active fault while in **Automatic** mode. |
| 2 | 4 | If TRUE, ''Command'' is dropped on an active fault while in **Manual (On)** mode. |
| 3 | 8 | If TRUE, an ''EmergencyShutdown'' that coincides with a start request is also reported as a **Failure** alarm. |
| 4..15 | - | Unused. |

===== Outputs =====

^ Name ^ Data Type ^ Description ^
| Command | bool | Operational command output (TRUE = Run, FALSE = Stop). |
| CompositeState | uint | Bit array describing the complete internal state of the block (see table below). |
| OperatingHours | time | Total accumulated running time (retained). Reset by ''OperatingHoursReset''. |
| StartCounter | udint | Total number of starts (retained). Reset by ''OperatingHoursReset''. |

Being a ''BaseAlarmBlock'' descendant, the block also provides the inherited **alarm interface** (''AlarmsInterface'' / ''Reset''/''Acknowledge''/''GetActiveAlarmsMask''…) used to chain its two internal alarms into the project alarm system.

**Description of CompositeState output values**
^ Bit ^ Mask ^ Meaning ^
| 0 | 1 | Command is active. |
| 1 | 2 | Feedback is active (Feedback = 1, or Feedback = 2 while Command is active). |
| 2 | 4 | Manual mode is active (OperatingMode ≠ Automatic, or a manual hardware override is reported). |
| 3 | 8 | Manual On is active (OperatingMode = On, or manual override while running). |
| 4 | 16 | Demand is active. |
| 5 | 32 | Kick (periodic exercise) is currently active. |
| 6 | 64 | Run-down (overrun) is currently active. |
| 7 | 128 | A flagged alarm is present. |
| 8..9 | - | Current OperatingMode representation. |

===== Detailed Function Description =====

The block runs an internal state machine (Off → WaitForFeedback → On → Run-Down, with parallel Failure, Kick and Emergency branches) and manages **two alarms**:

  * **Not Run (Fail to Start):** raised if ''Command'' is issued but ''Feedback'' does not become active within ''FeedbackTimeout''. Priority = ''NotRunAlarmPriority''.
  * **Failure:** raised by the external ''Failure'' input (and optionally by ''EmergencyShutdown'', see ControlFlags bit 3). Priority = ''FailureAlarmPriority'' / ''EmergencyAlarmPriority''.

Core capabilities:

  * **Operating Modes:** Automatic, Manual On, Manual Off. ''Off'' is dominant; ''EmergencyShutdown'' overrides all modes.
  * **Feedback Monitoring:** verifies the device actually started; if ''Feedback'' = 2 the feedback logic is bypassed and the running state mirrors ''Command''.
  * **Run-Down (Overrun):** after ''Demand'' is removed in Automatic mode the device keeps running for ''RunDown'' (e.g. to dissipate residual heat) before stopping. A device that never reported feedback, or that is dropped on the very first cycle, skips the run-down.
  * **Periodic Kick (Exercise):** in Automatic mode, if the device has been idle for ''KickFunctionInterval'', it is run for ''KickFunctionDuration'' to prevent mechanical seizing. The kick has its own feedback supervision.
  * **Emergency Shutdown:** sets ''Command'' = FALSE immediately, regardless of mode. If configured (ControlFlags bit 3), a coinciding start request raises a Failure alarm.
  * **Fault reaction:** ControlFlags bits 1/2 decide whether ''Command'' is dropped on a fault separately for Automatic and Manual modes (e.g. keep a critical pump running on a soft alarm in Manual).
  * **Maintenance Counters:** accumulated ''OperatingHours'' and ''StartCounter'', resettable via ''OperatingHoursReset''.

**Execution logic:** In Automatic mode a start is requested by ''Demand''; in Manual On it is forced. On a start the block enters //WaitForFeedback//, asserts ''Command'' and waits up to ''FeedbackTimeout'' for ''Feedback''. On success it goes //On// and increments ''StartCounter''; on timeout it raises the **Not Run** alarm. A ''Failure'' input or ''EmergencyShutdown'' diverts to the corresponding branch at any time. When ''Demand'' clears, the //Run-Down// branch keeps the device running for ''RunDown'' before final stop.

===== Application Example from a Real Project =====

**Scenario: Redundant refrigerant pump to the ice-rink floor collector**

Two pumps (M4/M5) circulate refrigerant to the floor. Each pump is driven by its own ''SwitcherBlock'':

  * The lead/lag demand from the twin-pump logic is wired to **//Demand//**; a differential-pressure switch (dP) is mapped to **//Feedback//** via ''BOOL_TO_USINT''.
  * If the PLC asserts ''Command'' but no dP appears within **//FeedbackTimeout//** = ''T#10s'', a **Not Run** alarm flags a broken coupling or seized rotor and the twin-pump logic can switch to the standby pump.
  * A motor-protection / inverter fault is wired to **//Failure//**; with ControlFlags bit 1 set, the pump's ''Command'' is dropped on fault in Automatic mode.
  * To avoid seizing during summer standstill, **//KickFunctionInterval//** = ''T#7d'' and **//KickFunctionDuration//** = ''T#30s'' exercise the pump weekly.
  * A short **//RunDown//** keeps refrigerant moving briefly after the demand stops.

''Command'' drives the pump relay; ''AlarmsInterface'' is chained into the machine-room alarm aggregator, and ''OperatingHours'' / ''StartCounter'' feed the maintenance view.

===== Versions =====

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