Chapter 3 Instruction Set Architectures

Chapter 3 Instruction Set Architectures Images courtesy of Addison Wesley Longman, Inc. Copyright 2001 Chapter Outline

Programming Languages Assembly Languages Instruction Set Architecture Design

A Relatively Simple ISA ISA of the 8085 microprocessor Images courtesy of Addison Wesley Longman, Inc. Copyright 2001 Programming Languages

High level languages Assembly languages Machine languages

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Assembly Language Attributes Instruction types

Data types Addressing modes Instruction formats Images courtesy of Addison Wesley Longman, Inc. Copyright 2001 Instruction Types

Data transfer Data operation Program control

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Numeric (integer, floating point) Boolean (true, false) Character (ASCII, Unicode) Images courtesy of Addison Wesley Longman, Inc. Copyright 2001 Addressing modes - Direct

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Addressing modes - Register Direct Images courtesy of Addison Wesley Longman, Inc. Copyright 2001 Addressing modes - Register Indirect

@R Images courtesy of Addison Wesley Longman, Inc. Copyright 2001 Addressing modes Immediate Images courtesy of Addison Wesley Longman, Inc. Copyright 2001

Addressing modes - Implicit Images courtesy of Addison Wesley Longman, Inc. Copyright 2001 Addressing modes - Relative

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More operands = less instructions More operands = larger words Images courtesy of Addison Wesley Longman, Inc. Copyright 2001 3-operand Instructions

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Instruction set Register set Memory access information

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Completeness Orthogonality Register set design Images courtesy of Addison Wesley Longman, Inc. Copyright 2001

ISA Requirements Backward compatibility?

Data types/sizes Interrupts? Conditional instructions? Images courtesy of Addison Wesley Longman, Inc. Copyright 2001 A Relatively Simple ISA Registers

Accumulator AC General purpose register R Flag Z

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A Relatively Simple ISA Instruction Set (continued) Images courtesy of Addison Wesley Longman, Inc. Copyright 2001 A Relatively Simple ISA Instruction Formats Images courtesy of Addison Wesley Longman, Inc. Copyright 2001

Example Relatively Simple Program 1 2 ... n, or n i

i 1 This could be written as a high-level language code snippet as follows. total=0; FOR i=1 to n DO {total = total + i}; 1. total = 0, i = 0

2. i = i + 1 3. total = total + i 4. IF i n THEN GOTO 2 Images courtesy of Addison Wesley Longman, Inc. Copyright 2001 Example Relatively Simple Program Code

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A Relatively Simple ISA Analysis Completeness

Orthogonality Register set design Images courtesy of Addison Wesley Longman, Inc. Copyright 2001 The 8085 ISA - Registers Accumulator A

General purpose registers B, C, D, E, H, L Stack pointer SP Flags S, Z, P, CY, AC Images courtesy of Addison Wesley Longman, Inc. Copyright 2001

The 8085 ISA - Instruction Set Data movement instructions Images courtesy of Addison Wesley Longman, Inc. Copyright 2001 The 8085 ISA - Instruction Set

Data operation instructions Images courtesy of Addison Wesley Longman, Inc. Copyright 2001 The 8085 ISA - Instruction Set Program control instructions

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n 1 2 ... n, or i i 1

1. i = n, sum = 0 2. sum = sum + i, i = i - 1 3. IF i 0 THEN GOTO 2 4. total = sum Images courtesy of Addison Wesley Longman, Inc. Copyright 2001 Example 8085 Program Code

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The 8085 ISA - Analysis Completeness Orthogonality

Register set design Images courtesy of Addison Wesley Longman, Inc. Copyright 2001 Summary Programming Languages ISA Design

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