This change in frequency is negligible, but it adds up. The issue with these crystals is that their oscillation frequency is affected by external temperature. Most RTC modules, such as the DS1307, require an external 32kHz crystal oscillator for timekeeping. Temperature Compensated Crystal Oscillator(TCXO)

This clock output may be useful in some applications for measuring clock timing accuracy or clocking other circuits. The INT/SQW pin on the DS3231 provides either an interrupt signal (due to alarm conditions) or a nice square wave at 1Hz, 4kHz, 8kHz, or 32kHz.Īdditionally, the DS3231 outputs a stable (temperature compensated) and accurate reference clock on the 32K pin. It also has two time-of-day alarms that can be programmed. It can work in either a 12-hour or 24-hour format and has an AM/PM indicator. For months with fewer than 31 days, it automatically adjusts the date at the end of the month, including leap year corrections (valid up to 2100). The DS3231 can keep track of seconds, minutes, hours, days, dates, months, and years.