How Does A Chip In A Battery Driven Watch Work ?

Usually, it works pretty well.

Like the chip in any electronic device, the chip in a watch is designed to contain the circuitry required to make the device function. Depending on the functions the watch has, such circuitry may include any or all of

• power regulator
• oscillator
• frequency divider
• motor driver
• display decoder
• display driver
• button interface
• logic for decoding month, day, year, day of the week, AM/PM, leap year, daylight savings time, low-battery indication, and other functions.

A watch generally has some sort of oscillator or resonator that oscillates at a fixed frequency determined by its physical characteristics. There is often some sort of temperature compensation involved, so the frequency remains the same over the range of environments the watch may encounter.

The frequency of the oscillator (often in the neighborhood of 32 kilohertz) is divided to a lower frequency (1 Hertz) to run the second hand, or the seconds display. It is further divided to run the minutes and hours display. Additional logic is used to decode day, date, weekday, year, and whatever else the watch displays.

Alarm functions require alarm memory, a driver for the alerting device, and comparison logic for comparing the current time to the alarm setting.

If there are function buttons, circuitry interfaces with those to provide control of setting the watch or performing other functions (for example, calculation).

I realize that describing what's in there doesn't tell you much about "how it works." The nitty-gritty requires a certain amount of electrical engineering and/or semiconductor physics understanding, and the details depend on the watch functions you are interested in.