PDF datasheet for the Atmel AT89C1051, the smallest member of the 20-pin 8051-compatible family, offering 1 KB of flash, 64 bytes of RAM and an analog comparator.

Datasheet for the M48T18, a TIMEKEEPER device from ST that combines battery-backed static RAM with a real-time clock in one package.

Datasheet for the DS1307 serial real-time clock, provided as a 165 KB PDF. The chip keeps time and calendar data, communicates over the I2C bus, includes 56 bytes of…