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Ch5 official - Basic Computer Organization & Design 1...

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1 Computer Organization Computer Architectures Lab BASIC COMPUTER ORGANIZATION AND DESIGN • Instruction Codes • Computer Registers • Computer Instructions • Timing and Control • Instruction Cycle • Memory Reference Instructions • Input-Output and Interrupt • Complete Computer Description • Design of Basic Computer • Design of Accumulator Logic
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2 Computer Organization Computer Architectures Lab INTRODUCTION Every different processor has its own design (different registers, buses, micro-operations, machine instructions, etc) Modern processor is a very complex device It contains Many registers Multiple arithmetic units, for both integer and floating point calculations The ability to pipeline several consecutive instructions to speed execution Etc. However, to understand how processors work, use a simplified processor model This is similar to what real processors were like ~25 years ago
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3 Computer Organization Computer Architectures Lab THE BASIC COMPUTER The Basic Computer has two components, a processor and memory The memory has 4096 words in it 4096 = 2 12 , so it takes 12 bits to select a word in memory Each word is 16 bits long CPU RAM 0 4095 0 15
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4 Computer Organization Computer Architectures Lab INSTRUCTION S Instruction codes Program A sequence of (machine) instructions (Machine) Instruction A group of bits that tell the computer to perform a specific operation (a sequence of micro-operation) The instructions of a program, along with any needed data are stored in memory The CPU reads the next instruction from memory It is placed in an Instruction Register ( IR ) Control circuitry in control unit then translates the instruction into the sequence of microoperations necessary to implement it
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5 Computer Organization Computer Architectures Lab INSTRUCTION FORMAT Instruction codes A computer instruction is often divided into two parts An opcode (Operation Code) that specifies the operation for that instruction An address that specifies the registers and/or locations in memory to use for that operation In the Basic Computer, since the memory contains 4096 (= 2 12 ) words, we needs 12 bit to specify which memory address this instruction will use In the Basic Computer, bit 15 of the instruction specifies the addressing mode (0: direct addressing, 1: indirect addressing) Since the memory words, and hence the instructions, are 16 bits long, that leaves 3 bits for the instruction’s opcode Opcode Address Instruction Format 15 14 12 0 I 11 Addressing mode
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6 Computer Organization Computer Architectures Lab ADDRESSING MODES Instruction codes The address field of an instruction can represent either Direct address: the address in memory of the data to use (the address of the
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This note was uploaded on 02/09/2012 for the course CSCI 504 taught by Professor Jon during the Spring '11 term at IUP.

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Ch5 official - Basic Computer Organization & Design 1...

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