Design Of A Real-Time Clock Chip

Real-Time Clock counts seconds, minutes, hours, date of the month, day of the weak, month and year with leap-year compensation. It has been widely used in industrial electronics and consumer electronics. I2C-bus is the Philips' patent. Many chips can be connected by only two wires. The Real-Time Clock Applied in I2C-bus discussed in this thesis not only provides time as basic function, but also has a built-in power sense circuit that detect power failures and automatically switches to the battery supply. This circuitry guarantees the accuracy of the Real-Time Clock when power-fail occurs or in other bad conditions. At the same time, there are 56 bytes of SRAM in the chip for important data storage. This chip supports a bi-directional, 2-wire bus and data transmission protocol. The data transmission rate is up to 100kb/s. Programmable squarewave ouput signal can be provided by this chip. At first, this thesis introduces the block diagram and pin description. The oscillator circuitry is based on the Pierce oscillator. The common voltage comparators are used to form power management module. The interface circuitry is designed to meet the requirements of I2C protocol. With the help of delay time, control logic accomplish the demand of sequential circuitry. The principle of the real-time clock is illustrated by week register. The stand 6-T cells are adopted to form RAM. During the analysis of system simulation, the address bus, the data bus and the write/read signals are explained in detail. At the end of this thesis, the design results of the chip are summarized. The 0.6um CMOS Double Poly Double Metal process is used to fabricate this chip. Under the Cadence software environment, we draw the schematics, simulated the circuit and completed the layout. Up to now, the chip has been fabricated. After testing, all functions meet the requirements.