Hi Vusi,

the RTC tutorial is not accurate, but the error should always be below 1%.

Maybe you use a crystal with a different frequency and you repeat not the calculations for your crystal.


If you like mathematics and have understand the tutorial, you can do the next step to get more precision:

http://www.specs.de/~danni/ap.../index.htm


If you want to toggle a port pin every minute, it can also be done by moving the LSB of the minute value to the port pin:

loop:
mov a, minutes
mov c, acc.0
mov p0.0, c
sjmp loop

On using P0 have you also add a pull up resistor on P0.0 ?


Peter