UT_RUN_LIMIT — A run limited by time or volume, or held by a remote signal

Runs a piece of equipment for a set time, until a set volume has gone through, or
for as long as a remote signal is held, and says why the run ended. Typical uses: an
effluent or irrigation run ("50 m³ or 2 h, whichever first"), filling a trough,
flushing a line, running a generator for a set time, a SCADA schedule that holds a
run signal.

RunCmd asks the equipment to run: wire it to a UT_PUMP's Demand (or a
motor's AutoCmd). The pump block still decides whether it is safe to run; this block
only decides how long.

Pins

Record UT_RUN_LIMIT_DATA

End reasons

The shared reasons of conventions. The words carry
no numbers: how far the run got is in elapsed and delivered (lastDuration and
lastVolume for the last run), and the limits in runTime and targetVolume.

Status

How it works

• A run starts on a rising edge of Start, cmdStart or RunHeld, if Permit is
  TRUE, Abort is FALSE and the settings are valid. A start while a run is active is
  ignored; Stop wins over a start in the same scan. A held Start acts once.
• Time counts only while Running is TRUE: a pump trip or restart delay pauses the
  run, and it carries on when the pump runs again (maxPause can end it).
• The volume is the rise of Volume since the start. A total that goes down (reset)
  or reads not-a-number is handled: the run carries on from the new value, never
  counting backwards. A total that is not a number when the run starts is not
  counted from 0: the run counts from the first valid reading.
• The first reason found ends the run: Stop, Abort, Permit, RunHeld dropping, lost
  comms, an invalid setting, the limit, maxPause.

After a power cut

An irrigation run on a sports field or a property often has no operator: when the
power comes back (or the PLC is stopped and started) the run should carry on, as a
commercial irrigation controller does. powerUp chooses:

• A RunHeld that was already on at the cut and had been dealt with (its run
  done, or the start refused) does not start another run after the power cut, in any
  mode: as without a power cut, it must go off and on again. Only a RunHeld that
  came on while the power was off counts as a new request.
• A run that carries on keeps its running time and volume: time spent before the cut
  is not counted again, and the run never goes past runTime or targetVolume (a
  run already at its limit ends at once, Done). The volume carries on from where
  the Volume total reads at power-up, so a total that came back lower (a totaliser
  saved every 12 h) is not counted backwards.
• The resumed run starts from its last save: the progress is saved when the run
  starts and ends, and every progressSave (default 1 min) while it is active, never
  every scan (flash wear: a few hundred saves on a day of irrigation, none when idle).
  So up to progressSave of running can be given again after a cut.
• A run ended at power-up (UT_STOP_REMOTE_OFF, UT_STOP_POWER_CUT) is a run end:
  Done is on for that scan, runs counts it, and it becomes the last-run summary.
• Permit, Abort, CommsOk and the limits are checked from the first scan: a run
  that carries on with Permit FALSE ends at once, as it would without a power cut.
• Kept over a power cut (inside the block): the last run's summary, saved once
  at each run end; and the progress of a run in progress (whether one is, whether
  RunHeld started it, whether RunHeld is on, its running time and volume), saved
  as above and when RunHeld changes.

Using it

IrrRun(Start := StartPB, Stop := StopPB, RunHeld := ScadaRun, Abort := SumpLow,
       AbortCode := UT_STOP_LOW_LEVEL, Running := P1.Running, Volume := FlowTot.Total, CommsOk := NOT ScadaWd.CommsFail,
       Data := IrrRunCfg);
P1(Demand := IrrRun.RunCmd, Running := M1.Running, MotorReady := M1.Ready, MotorAuto := M1.Auto,
   Data := P1Data);

With IrrRunCfg.byTime := TRUE, byVolume := TRUE, runTime := T#2h,
targetVolume := 50.0, the run ends at 50 m³ or 2 h of pumping, whichever comes
first (endReason UT_STOP_DONE), or when the sump runs low (UT_STOP_LOW_LEVEL,
with delivered showing how much went, e.g. 32.4 m³).