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Lecture on Microcomputer. Presented By WWW.AssignmentPoint.Com. 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 Typically 20 to 32 bit long
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Lecture on Microcomputer Presented By WWW.AssignmentPoint.Com www.assignmentpoint.com
What is Microcomputer? www.assignmentpoint.com
Typical Microcomputer Architecture www.assignmentpoint.com
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 www.assignmentpoint.com
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. www.assignmentpoint.com
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 www.assignmentpoint.com
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) www.assignmentpoint.com
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 www.assignmentpoint.com
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 www.assignmentpoint.com
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. www.assignmentpoint.com
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 www.assignmentpoint.com
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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 www.assignmentpoint.com
Assembly Language Instruction Format • Three address • Two address • One address • Zero address CLD ; clear direction NOP ; No operation For all microprocessors www.assignmentpoint.com
