Calendar freeze

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Typical freeze screen (SP-S2) on startup.


A freeze at startup on the shown screen (with no cyclic reset) is caused by the RTC not outputing a time pulse at all.

The system ROM doesn't give a CALENDAR ERROR in this particular case because of a programming oversight.


  • Check battery voltage
  • Check 32768Hz crystal
  • Check uPD4990 traces, especially power and pin 11 (TP)
  • Check NEO-F0 interface pins
  • Check 74HC32 and traces to uPD4990
  • Try to reset Backup RAM content:
    • Either remove battery
    • Or flip all dip switches to on and then power on the board. Then turn off the board and return all dips to normal settings
  • You can use unibios to skip this error