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. The MCU was actually the first "system-on-chip" (SoC) but that term was coined later when more components were added. See SoC
, flash memory
They Don't Get the Publicity
Because MCUs contain only 8-, 16- or 32-bit CPUs and cost just a few dollars or even less than one dollar, they do not get the mainstream attention as do the latest 64-bit chips in a PC or graphics card, which cost several hundred dollars. MCUs also do not require the state-of-the-art chip technology (see process technology
However, MCUs are everywhere, embedded in products from toys to appliances and just about anything. New cars can employ hundreds. For example, an entire MCU might be dedicated to a simple task such as waiting for the car door to open or close. See embedded system
and automotive systems
Maybe Five Computers in the World
In 1943, Tom Watson, the founder of IBM said "I think there is a world market for maybe five computers." With tens of billions of microcontrollers shipped every year, each of which contains a CPU at least a thousand times more powerful than any computing device of that era, one might say predicting future computer technology can be tricky at best.
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 PIC brand microcontrollers from Microchip are used in myriad applications, cost less than 50 cents each and are a lot more powerful than the Motorola 6801 (previous image). We're not great at predicting technology. In 1949, Popular Mechanics speculated that future computers would only weigh "one and a half tons!"
A Microcontroller Behind Everything
Today's cars can have more than a hundred MCUs, each one controlling the simplest function from pressing a button to more complicated systems like the ones in the Honda above.