UT_FLASHER — On/off pulse generator

A flashing lamp, a horn that pulses, or an "every 10 minutes, do this" trigger.

Pins

How it works

• Q is off whenever Enable is off. When Enable comes on, the first phase starts
  at once: ON with StartOn TRUE (and a Pulse), or OFF for OffTime with StartOn FALSE.
• Turning Enable off stops at once. Turning it on again starts again from the first
  phase, and Cycles starts again from 0. Cycles keeps its last value while Enable is off.
• No drift. Each phase is timed from when it should have started, not from the
  scan that noticed it. After 10,000 cycles the ON phases still start at exact
  multiples of OnTime + OffTime.
• A change of OnTime or OffTime acts on the phase running now. Shortening the ON
  time below the time already on turns Q off on the next scan.
• OnTime = 0: Q stays off and only Pulse fires, every OffTime.
  OffTime = 0: Q stays on and Pulse fires every OnTime. Both 0: Pulse
  fires every scan. A negative time counts as 0. Very long times are fine.
• Q and Pulse can change at most once per scan. If a cycle is shorter than the
  task interval, Cycles still counts every cycle.
• Hold stops the cycle's clock and turns Q off. When Hold drops, the phase
  carries on where it stopped: a stirrer blocked at minimum level gets the rest of
  its ON phase once the level is back, and an OFF phase is lengthened by the time
  held. ET, Remaining and NextOnIn stand still while held (NextOnIn stays
  0 when the hold came in an ON phase: that phase is still to finish).
• StartNow (rising edge) starts an ON phase at once, with a Pulse, and the
  cycle is timed from it. A held StartNow acts once. While Hold is on, the ON
  phase starts when Hold drops.
• ET, Remaining and NextOnIn are all T#0s while Enable is off. Show them
  with UT_TIME_TEXT.