Отправлено MPA 06 июня 2003 г. 11:51 В ответ на: Подскажите по DS1307. Надо ли ей к кварцу конденсаторы по 20пФ вешать, или нет? У меня и так, и эдак отлично работает.(+) отправлено только учусь 06 июня 2003 г. 10:47

X1, X2 – Connections for a standard 32.768kHz quartz crystal. The internal oscillator circuitry is
designed for operation with a crystal having a specified load capacitance (CL) of 12.5pF.
For more information on crystal selection and crystal layout considerations, please consult Application
Note 58, “Crystal Considerations with Dallas Real-Time Clocks.” The DS1307 can also be driven by an
external 32.768kHz oscillator. In this configuration, the X1 pin is connected to the external oscillator
signal and the X2 pin is floated.
CLOCK ACCURACY
The accuracy of the clock is dependent upon the accuracy of the crystal and the accuracy of the match
between the capacitive load of the oscillator circuit and the capacitive load for which the crystal was
trimmed. Additional error will be added by crystal frequency drift caused by temperature shifts. External
circuit noise coupled into the oscillator circuit may result in the clock running fast. See Application Note
58, “Crystal Considerations with Dallas Real-Time Clocks” for detailed information.
Please review Application Note 95, “Interfacing the DS1307 with a 8051-Compatible Microcontroller”
for additional information.

Кварц нужно правильный, а дополнительные конденсаторы только ухудшат точность.