Motorola MCU MC9S12DP256 Instrukcja Użytkownika Pobierz pdf (Strona 3)

Above is a diagram of the HCS12’s register set. Familiarize yourself with these registers

and what each is used for. Read section 2.1 of the “CPU12 Reference Manual” which

gives a good description of them. Having a good understanding of the register set is

crucial to effectively performing assembly language programming.

Assembly Language

By this point in your education you should be familiar with computer programming in a

high-level language such as C, C++ or Java. Such languages are useful because they

abstract the programmer from the details of a computer’s hardware. Programs written in

high-level languages are written in a format that closely resembles English and are easy

to understand. Once a program is written in a high level-language, it is run through a

compiler that takes the source code and translates it into machine code. While high-level

languages do have advantages, the compilation process introduces inefficiencies at the

machine code level. For many applications, this does not create a problem. However for

time critical programs, assembly code is often used to avoid such inefficiencies as it is

only slightly abstracted from machine language.

You will have to make an effort (especially at the beginning) to become familiar with the

assembly commands (or instruction set) for the HCS12. A instruction set summry can be

found on pages 6-20 of the “CPU12 Reference Manual.” Section 6 of the reference

manual contains the detailed description of all the instructions you may need. Each

instruction will have its own page that looks like:

1 2 3 4 5 6

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Motorola MCU MC9S12DP256 Instrukcja Użytkownika Strona 3