Hi!
I have try to designed software RTC several time, but i always get result diffrent then calculation. Even simulator shows perfect result the output of actual circuit is different. When i think about it, i only see that it can be due to slight diffrence of crystal. Now my questions are,
1, How we can trim crystal oscillator for slight frequency adjustment. I know it can be done by small variable capacitor, but how i don't know. Can any one tell me about it.
2, What can happen if i donot use the 2 capacitors used across crystal. Do they shift frequency.
3, If we use 89C51, How much accurate software RTC can be built without adjusting each unit seperately. The one i build is 15 sec behind normal time in 24hours.
Thanks!