Datasheet

Chapter 1.
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Overview
1.1. Overview of Microcontrollers
A microcontroller is a microprocessor intended for embedded
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applications.
Microcontrollers differ from traditional microprocessors in a few key ways:
1. Microcontrollers generally are totally self-contained, requiring no external support other than power
and sometimes a clock source.
2. Microcontrollers generally include non-volatile program memory so that the program need not be read
from external media during startup. Most commonly, microcontrollers incorporate Flash memory for
program storage.
3. Microcontrollers are generally Harvard Architecture processors rather than traditional von Neumann
processors. The Harvard Architecture allows for different memory widths between the data and
program memory, and the separate busses allow data and program instructions to be fetched during
the same instruction cycle.
4. Embedded applications often require a high degree of detrminism. To support this, most
microcontrollers execute all or most instructions in the same number of clock cycles. In contrast,
microprocessors such as the Intel family may execute some instructions in just a few cycles, while
others take dozens.
5. Microcontrollers tend to use most of their pins for I/O. In contrast, microprocessors tend to use their
pins for data busses, multi-phase clocks, cache memory, and other, non-application purposes.
6. Microcontrollers frequently have a variety of available peripherals internal to the part. Serial ports, I2C
interfces, analog to digital converters and the like are common. Microprocessors tend to have a few
general putpose I/O pins, if that.
7. Micocontrollers typically have a number of power saving features, and often require very little power.
Compare a typical dsPIC, requiring about 150 milliwatts at full speed with a typical PC microprocessor
requiring 70 or more watts. And the dsPIC has features allowing it to reduce its power requirement to
the nanowatt range for some applications. In many embedded applications the microcontroller current
is less than the internal leakage current of the battery.
8. Microcontrollers tend to be inexpensive, ranging from around a quarter to perhaps ten dollars. Refer to
Appendix E, Microchip PIC Families for examples. Microprocessor prices range from a few dollars to
several hundreds of dollars. As of this writing, the suggested price for Intel's i7-3940XM is $1096.
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embedded system n. A combination of computer hardware and software, and perhaps additional mechanical or other parts,
designed to perform a dedicated function. In some cases, embedded systems are part of a larger system or product, as in the case
of an antilock braking system in a car.[Barr]