pic 18f internal osc

[richard.c]

Hi All,

Just wondered if anyone had succeeded in using the 18F chips internal 31k hz oscillator as a replacement for a 32k external crystal in a Real Time Clock.

Have seen some old postings saying it could be done, but nothing currently showing and my own coding attempts out by several mins per day - chip running at 4 meg.

I'd love to know why Microchip specifically produced a divider to that frequency if it was not intended for a RTC

thanks

Richard

 

[Nigel Goodwin]

Hi All,

Just wondered if anyone had succeeded in using the 18F chips internal 31k hz oscillator as a replacement for a 32k external crystal in a Real Time Clock.

Have seen some old postings saying it could be done, but nothing currently showing and my own coding attempts out by several mins per day - chip running at 4 meg.

I'd love to know why Microchip specifically produced a divider to that frequency if it was not intended for a RTC

It's presumably just an RC oscillator?, so useless as a real time clock source. It's 32KHz simply because that's the common frequency to use for low power consumption - the lower the speed, the lower the power used.

 

[blueroomelectronics]

It's not accurate enough for a clock, it's 1% and 31250Hz not 32768Hz