RTC Memory - mhightower83/Arduino-ESP8266-misc GitHub Wiki

Espressif reference in SDK

System time will return to zero because of system_restart, but RTC still goes on.

If external hardware resets the chip via EXT_RST or CHIP_EN (such as timed wake-up from Deep-sleep), the RTC timer will be reset. However, RTC Memory may continue.

  • Reset by pin EXT_RST
    • RTC memory won’t change
    • RTC timer starts to zero
  • Watchdog reset
    • RTC memory won’t change
    • RTC timer won’t change
  • system_restart
    • RTC memory won’t change
    • RTC timer won’t change
  • Power-on
    • RTC memory contains a random value
    • RTC timer starts from zero
  • Reset by pin CHIP_EN
    • RTC memory contains a random value
      • Empirical observation: With brief reset pulses to CHIP_EN, data appeared to remain valid. This may not be immediate - TODO: evaluate This might be the way the five power on/offs method can detect a reset to factor is being requested.
    • RTC timer starts from zero