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Definition: microcontroller


A single chip that contains the processor (CPU), non-volatile memory (flash memory or ROM) for the program, volatile memory (RAM) for processing the data, a clock and an I/O control unit. Microcontroller units (MCUs) are available in numerous sizes and architectures, and billions of these "computers on a chip" are embedded each year in products from toys to appliances to automobiles. For example, new cars can employ a hundred or more, each one very often assigned the simplest of tasks such as monitoring a single button on the dashboard to trigger an event when the driver presses it (see embedded system and automotive systems). See CPU, RAM, ROM and clock.






Motorola 6801 - One of the First
Introduced in 1978, the 6801 was one of the first semiconductor products to claim the "computer on a chip" moniker. These magnified images show the entire chip (top), about three quarters of the 256 bytes of RAM (left) and only a few bytes at 400x.






They Don't Get Much Smaller
These 8-bit microcontrollers from Microchip are used in myriad applications, cost less than 50 cents each and are much more powerful than the 6801. We're not great technology predictors. In 1949, Popular Mechanics speculated that future computers would only weigh "one and a half tons!"