Example 21 48 the arm architecture if the thumb

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Unformatted text preview: age Programming Summary of chapter contents The ARM processor is very easy to program at the assembly level, though for most applications it is more appropriate to program in a high-level language such as C or C++. Assembly language programming requires the programmer to think at the level of the individual machine instruction. An ARM instruction is 32 bits long, so there are around 4 billion different binary machine instructions. Fortunately there is considerable structure within the instruction space, so the programmer does not have to be familiar with each of the 4 billion binary encodings on an individual basis. Even so, there is a considerable amount of detail to be got right in each instruction. The assembler is a computer program which handles most of this detail for the programmer. In this chapter we will look at ARM assembly language programming at the user level and see how to write simple programs which will run on an ARM development board or an ARM emulator (for example, the ARMulator which comes as part of the ARM development toolkit). Once the basic instruction set is familiar we will move on, in Chapter 5, to look at system-level programming and at some of the finer details of the ARM instruction set, including the binary-level instruction encoding. Some ARM processors support a form of the instruction set that has been compressed into 16-bit Thumb' instructions. These are discussed in Chapter 7. 49 50 ARM Assembly Language Programming 3.1 Data processing instructions ARM data processing instructions enable the programmer to perform arithmetic and logical operations on data values in registers. All other instructions just move data around and control the sequence of program execution, so the data processing instructions are the only instructions which modify data values. These instructions typically require two operands and produce a single result, though there are exceptions to both of these rules. A characteristic operation is to add two values toget...
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This document was uploaded on 10/30/2011 for the course CSE 378 380 at SUNY Buffalo.

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