The DS3231 is a low-cost, high-precision I2C real-time clock (RTC) with integrated temperature-compensated crystal oscillator (TCXO) and crystal. The device contains a battery input to maintain timing when main power is removed. Integrated crystals improve device longevity and reduce component count in production lines. The DS3231 is available in commercial and industrial temperature ranges and is offered in a 16-pin 300-mil SO package. The RTC stores seconds, minutes, hours, day of the week, date, month, and year information. Months with fewer than 31 days are automatically adjusted at the end of the month, including leap year corrections. The clock can operate in either 24-hour or 12-hour format with AM/PM indication. It provides two programmable calendar alarms and a programmable square wave output. Address and data are transmitted serially through the I2C bidirectional bus. A temperature-compensated voltage reference and comparator circuit monitor Vcc status, detect power supply failures, provide a reset output, and automatically switch to backup power when necessary. The RST monitor pin can be used as a manual input to generate a system reset. In addition to its high timing accuracy, the DS3231 includes a digital temperature sensor accessible via the I2C interface. The accuracy of this temperature sensor is ±3°C. On-chip control circuitry enables automatic power supply detection and manages power switching between primary power and backup power (such as a low-voltage battery). If the main power supply is lost, the device continues to provide accurate timing and temperature data without performance degradation. An on-chip reset function can restart the system microprocessor when main power is restored or when the voltage returns to an acceptable range.