UT_TONR — Retentive accumulating timer

Like a TON, except the elapsed time is kept when In goes off, and timing
continues from there. Like Siemens TONR and Rockwell RTO, it lives for as long as
the PLC is powered: after a power cycle ET starts at 0. Typical uses: time a
condition has existed, accumulated treatment time within a run.

Pins

How it works

• While In is on, time adds up; while it is off, ET holds. Q comes on when the
  total reaches PT and stays on until Reset.
• Reset clears the time. Held with In on, nothing is gathered; timing starts from 0
  when Reset releases.
• PT lowered below the time already gathered: Q comes on at once (ET shows PT).
  PT raised again: Q goes off and timing carries on from the time gathered.
• PT of 0 (or negative): Q comes on as soon as In is on, not before.
• Nothing is retained. After a power cycle or a PLC restart, ET is 0 and Q is off.
• Accuracy: each period In is on is counted to within one scan.

TOFR (retentive off-delay)

An output that stays on until x has been off for PT in total:

OffTimer(In := NOT x, PT := T#10m, Reset := ResetPB);
Out := NOT OffTimer.Q;