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438 UNDERSTANDING MICROCONTROLLERS

Figure 35- 1 Example low- cost
modular microcontroller, designed for
learning and experimentation. It contains
the microcontroller chip itself, plus a
liquid- crystal display, button joystick,
and other components.

8- 16- , OR 32- BIT ARCHITECTURE
As with your desktop computer, microcontrollers come with different data- processing archi-
tectures; these are denoted by the number of bits they process at one time.

• The oldest and simplest of microcontrollers used 4- bit processing. These are of little use to
us today, and, besides, they’re no longer common in the consumer chip- selling market-
places.
• On the other end of the spectrum are MCUs that handle 64 bits at a time. These are spe-
cialty chips used for high- end applications and, as such, tend to be expensive and more
difficult to program. (Of course, these limitations could and probably will change as time
marches on. That’s progress for you.)
• Middle- of- the- road microcontrollers handle 8, 16, or 32 bits at a time. The most common
for amateur robotics is the 8- bit variety, which, despite handling “only” 8 bits at a time, is
ideally suited to the vast majority of robot programming tasks. Eight- bit MCUs are the least
expensive and the most widely available.

Recall that the bit is the smallest value that can be stored in the memory of a microcontroller or
processed through its circuitry. A bit is either off or on. The two possible values for a bit are
G most commonly represented by the numerals 0 and 1. The value stored in the bit is not really a
numeric “zero” or “one”; the 0 and 1 are used as a kind of shorthand. Other shorthands
include LOW for 0 and HIGH for 1.

LANGUAGE PROGRAMMING
All microcontrollers need to be programmed for the task you want them to do. None “just
work” out of the box (exception: they come preprogrammed with a demo).
There are two general methods of programming a microcontroller, which, for the lack of
better terms, I’ll call low- level programmable and integrated- language programmable.
These loosely defined terms relate to how the programming is stored and executed in the
controller. Both kinds of microcontrollers are fully programmable.

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