A microcontroller unit (MCU) comprises the same basic ROM, RAM and CPU elements as a microprocessor (MPU) for less demanding tasks such as controlling a toy or a microwave oven. As these applications do not require the ultimate in speed or program complexity, MCU designs can be implemented with fewer components so that the complete function will fit on a single chip.
Gary Boone and Michael Cochran's 1971 design of Texas Instruments TMS1802 single-chip calculator device provided the foundation for the TMS1000 general-purpose 4-bit MCU family announced in 1974. Priced at $2 in volume, it powered burglar alarms, garage door openers, games, and toys such as "Speak and Spell" that introduced digital electronics to the consumer.
In 1976 both Intel and Mostek (3870) introduced 8-bit architectures that served more demanding applications in automobiles and PC peripherals. The Intel MCS-48 family offered both EPROM (8748) and masked-ROM (8048) versions. The EPROM version made MCUs practical for prototyping and low-volume production systems. (1971 Milestone) Intel's more powerful 1980 successor, the 8051, established a standard architecture that survives today in numerous variants for specific applications.
By the 1980s MCU architectures from European, Japanese and US manufacturers served numerous special-purpose applications. Bell Laboratories' MAC-4 met telecommunications needs. Motorola and Hitachi derived high-performance MCUs from the 68000 MPU. General Instrument's PIC family (today Microchip) won low-cost consumer designs. Hidden by the hundreds in appliances, automobiles, and personal electronics products, the MCU may be today's most ubiquitous semiconductor device.
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Franz, Gene (TI) an oral history (2009) Transcript in process
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Nunnally, C.E. "Teaching Microcontrollers," Frontiers in Education Conference, 1996. FIE '96. Proceedings of 26th Annual Conference, Vol. 1 (November 6-9, 1996) pp. 434-436.
Seitz, Frederick, and Einsprunch. Norman G. "1970s and the Microcontroller" Chapter 19 of Electronic Genie: The Tangled History of Silicon. (Urbana and Chicago, IL: University of Illinois Press, 1998) p. 229.