MCP7940N Real-Time Clock/Calendar (RTCC)
Microchip Technology MCP7940N Real-Time Clock/Calendar (RTCC) uses digital timing compensation for an accurate clock/calendar, a programmable output control for versatility, and a power sense circuit that automatically switches to the backup supply. Using a low-cost 32.768kHz crystal, it tracks time using several internal registers. For communication, the MCP7940N uses the I2C bus. The clock/calendar automatically adjusts for months with fewer than 31 days, including corrections for leap years. The clock operates in either the 24-hour or 12-hour format with an AM/PM indicator and settable alarm(s) to the second, minute, hour, or day of the week, date, or month. Using the programmable CLKOUT, frequencies of 32.768kHz, 8.192kHz and 4.096kHz and 1Hz can be generated from the external crystal. The device is fully accessible through the serial interface while VCC is between 1.8V and 5.5V, but can operate down to 1.3V for timekeeping and SRAM retention only.
