Page 372 - Introduction to Microcontrollers Architecture, Programming, and Interfacing of The Motorola 68HC12

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Other Microcontrollers

The microcomputer is a powerful tool, as we have learned in the preceding chapters. But
the microcomputer is more than just one type of computer. There is a wide variety of
microcomputers with different capacities and features that make them suitable for
different applications. This chapter gives you some idea of this variety and the
applications for which particular microcomputers are useful. To keep our discussion
within the scope of this book, we examine microcomputers that are related to the 6812.
This is particularly convenient for us since the 6812 is in the middle of the Motorola
family of microcomputers, so that being thoroughly familiar with the 6812 makes it
fairly easy to learn the other microcomputers in this family. This discussion of Motorola
microcomputers will also help you with microcomputers designed by other companies.
This chapter has two themes. The first consists of a discussion of Motorola
microcomputers that are simpler than the 6812, which include the 6811, the 6808, and
the 6805. The second theme is an overview of the 68300, 500, and M-CORE series,
machines more powerful than the 6812. After you read this chapter, you should be able
to write simple programs for the 6811,6808, and 6805 and their variants. You should be
able to answer such questions as: Where should a 32-bit, 16-bit, or 8-bit microcomputer
be used? You should be able to approach a microcomputer designed along quite different
lines than the Motorola family, with some idea of what to look for. You should
appreciate the capacities of different microcomputers, and you should be able to pick a
microcomputer that is suitable for a given application.
Although the 6805 came first historically, we will treat the 8-bit microcomputers in
order of their similarity to the 6812. We begin with a discussion of the 6811 followed by
the 6808 and 6805. The final sections cover the 68300, 500, and M-CORE series, and
observe the suitability of each microcomputer for different applications.

12.1 The 6811

The 6811, the immediate predecessor of the 6812, was designed for a specific application,
automotive control, and then made available for other applications. The 6812 is upward
compatible to the 6811. The register set for the 6811 is identical to that of the 6812. The

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