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System services

Two things a board can do without being asked: keep values across a power cut, and know what the time is. Both depend on a chip being fitted, and neither is configured in a project — if the hardware is there, the service is there.

The chips that a project does configure are in the peripheral catalogue.

Retentive values — surviving a power cut

Tags on the retain list are stored automatically according to what the board has fitted. There is nothing to configure.

The board has Behaviour
FRAM changes are stored within 1 s; no limit on the number of writes
EEPROM changes are stored within 5 minutes at the latest — this protects the chip's endurance, and even under constant change it lasts over 9 years
neither internal flash, stored within 10 s
  • The image in memory is protected by a checksum in two alternating copies. A power cut in the middle of a write can never damage both; after start-up the last complete state applies.
  • Changing the list of retained variables — a different project or version — means the variables start from their initial values, with a record in the diagnostics. Values are never mixed up between variables.
  • If the board's catalogue entry declares memory but the chip does not answer, the panel reports it and falls back to internal flash. Retention never simply stops working.
  • Capacity: 64 retained variables, or 16 without a memory chip fitted.

Counting pieces every cycle?

Then FRAM is the right choice. An EEPROM would only store it once every five minutes.

Real time

A board with a PCF8563 fitted, backed by a battery, knows the date and time even after being switched off. Alarms and diagnostics then carry the real time.

Setting the time:

  • Service cable: the settime tool sets it from the PC; without --apply it only prints the current time. The serial command VUT!2026-08-09 14:32:05 does the same directly.
  • WebVisu: the Set panel time button in the status bar takes the time from the phone or PC it is being viewed on. The button only appears on panels that support setting the time.

VUT! prints a source= and a state=:

  • rtc / ok — the time comes from the clock chip and survives a power cut
  • sys / none|invalid — there is no clock chip, or its battery is flat: the time is valid until the panel is switched off and starts again at 2000-01-01. A flat battery is reported by the diagnostics.

The time is local. The panel does not deal with time zones or daylight saving — when the clocks change, set it the way you set the machine.