I would like to ask you about the difference between Power On Reset[POR] and other Resets because in PIC18 controller datasheet i have seen a statement like:

Note 1: The RTCCFG register is only affected by a POR.

The RealTime Clock is affected by only POR it says.

What are the conditions in which the POR can happen to embedded systems ?

And I trust Watch dog reset and others just make the code run again from start address of program memory.

  • \$\begingroup\$ Don't trust : verify. Other resets won't affect the RTC but they may set other peripherals, interrupt flags or interrupt enables to a "safe" state. Databook should confirm or deny this. \$\endgroup\$
    – user16324
    Commented Feb 28, 2014 at 11:10

1 Answer 1


A Power-on Reset occurs when power is removed from the device and then reapplied. This can happen when the power source runs dry and is subsequently replaced or recharged or in blackout periods. Note that brownouts will result in a Brown-out Reset instead if the device is capable.


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