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Lecture 8

Lecture 8. Presented By Dr. Shazzad Hosain Asst. Prof. EECS, NSU. What is Microcomputer?. Typical Microcomputer Architecture . The Microcomputer Bus. Address Bus Information transfer one direction, microprocessor to memory or I/O elements, so unidirectional bus

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Lecture 8

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  1. Lecture 8 Presented By Dr. ShazzadHosain Asst. Prof. EECS, NSU

  2. What is Microcomputer?

  3. Typical Microcomputer Architecture

  4. The Microcomputer Bus • Address Bus • Information transfer one direction, microprocessor to memory or I/O elements, so unidirectional bus • Typically 20 to 32 bit long • Determines addressable memory, 1 MB to 4 GB

  5. The Microcomputer Bus • Data Bus • Bidirectional i.e. to or from microprocessor • Multiplexed / time shared data bus e.g. in 8086 20 bit address is send through 16-bit data bus and 4 status lines • Determines the word size of the microcomputer • Control Bus • Used to send control signals to synchronize the operation of individual microcomputer elements • Each microcomputer has a unique set of control signals.

  6. Clock Signals • Clock generator generates clock signals • Most MPs have external clock generator circuit • Each instruction requires a number of clock signals • Clock signals determines the speed of MPs • The short period cycle means clock speed is large, means high speed of computer

  7. The single chip microprocessor • Microprocessor is the CPU of the microcomputer • The main areas of microprocessor • Register section • The control unit • The arithmetic and logic unit (ALU)

  8. Basic Microprocessor Registers • Instruction Register (IR): stores instructions • Program Counter (PC): contains the address of the next instruction to be executed • Memory Address Register (MAR): contains address of data • Accumulator (A): typically a 8 bit register, used to store result after most ALU operations

  9. Accumulator based vs. general purpose based microprocessor • Accumulator based • Intel 8085 and Motorola 6809 are accumulator based. • Accumulator is used as one of the data source • Result goes to accumulator • Example: ADD R1 • General purpose based • Intel 8066/../Pentium are of this kind. • The registers contain hold data, memory address, results of ALU so on. • Example: ADD AX, BX, ADD [AX], BX

  10. Use of the Basic Microprocessor Registers • Let us add contents of two memory locations • For example, add [2010] = 0002 and [2012] = 005 • In general [NNNN] represents the content of the memory location NNNN.

  11. Steps of Addition of [2010]+[2012] • Load MAR with 2010 • Move contents of 2010 into data register, D0, which may be AX/BX etc. • Increment MAR by 2 to hold 2012 • Add D0 with [2012] and store the result into D0 Instruction set form Motorola 68000

  12. L E PC L E L E E L

  13. Microprogramming the Control Unit • Each instruction is executed by a set of microinstructions • The microinstructions has their own codes • The codes are stored into internal memory, called the control memory (ROM) • Let us increment a register by 1

  14. Assembly Language Instruction Format • Three address • Two address • One address • Zero address CLD ; clear direction NOP ; No operation For all microprocessors

  15. References • Chapter 6, Fundamental of Digital Logic and Microcomputer Design – by M. Rafiquzzaman • 6.1, 6.2, 6.3, 6.6.3

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