This project uses a Microchip PIC microcontroller, a serial EEPROM and a thermistor to create a temperature recorder. The temperature is measured and stored at user programmable intervals; this can be from 1 second to 256 seconds. The time interval is set by programming it and the start time into the EEPROM. The PIC is a 12F683 device and runs at 4 MHz using the internal oscillator. The I2C interfaces run at nearly 100 kHz using bit-banging (programmed control of the I/O lines) and not a PIC SSP interface.
Source: Andrew M. Bishop