Page 12 - Embedded Microprocessor Systems Real World Design

lntroduction

Imagine this scene: You get into your car and turn the key on. You take a 3.5” floppy
disk from the glove compartment, insert it into a slot in the dashboard, and drum
your fingers on the steering wheel until the operating system prompt appears on
the dashboard liquid crystal display (LCD). Using the cursor keys on the center
console, you select the program for the electronic ignition, then turn the key and
start the engine. On the way to work you want to listen to some music, so you insert
the program compact disc (CD) into the player, wait for the green light to flash
indicating that the digital signal processor (DSP) in the player is ready, then put in
your music CD.
You get to work and go to the cafeteria for a pastry. Someone has borrowed
the mouse from the microwave but has not unplugged the microwave itself, so the
operating system is still up. You can heat your breakfast before starting work.
What is the point of this inconvenient scenario? This is how the world would
work if we used microprocessor technology without having embedded microprocessors.
Every microprocessor-based appliance would need a disk drive, some kind of input
device, and some kind of display.
Embedded microprocessors are all around us. Since the original Intel 8080 was
pioneered in the 1970s, engineers have been embedding microprocessors in their
designs. They even are embedded in general-purpose computers; if you own a vari-
ation of the IBM PC/AT, there is an embedded microprocessor in the keyboard.
Virtually all printers have at least one microprocessor in them, and no car on the
market is without at least one under the hood. Embedded microprocessors may
control the automatic processing equipment that cans your soup or the controls of
your microwave oven. Basically, we can define an embedded microprocessor as
having the following characteristics:

Dedicated to controlling a specific real-time device or function.
Self-starting, not requiring human intervention to begin. The user cannot tell if
the system is controlled by a microprocessor or by dedicated hardware.
Self-contained, with the operating program in some kind of nonvolatile memorv.

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