Microcomputer System Architecture

Blocks of Microcomputer System

CPU consists of

• Registers for the temporary storage of information
• ALU for performing operations on this information
• Instruction decode and control unit that determine the operation to perform
• Instruction Register (IR) holds the binary code for each instruction as it is executed
• Program Counter (PC) holds the memory address of the next instruction to be executed

RAM

• Read Write memory. It is volatile.
• User program and data are loaded in to RAM for execution

ROM

• Read only memory. It is non-volatile
• Is used to hold software routines that perform input/output operations

Buses

• Unidirectional Address Bus to point memory location
• Bidirectional Data Bus to read/write data in memory
• Control Bus to generate read, write and synchronization signals

Interface Circuits

• Provide circuitry to connect peripheral devices

Peripheral Devices

• Human interface device like keyboard, mouse, printer, etc.
• Storage device like hard disk, optical disks, USB, etc.
• Control and Monitor devices

Software

• Input / Output Subroutines: Directly manipulate the hardware of the system
• Operating System for managing hardware resources
• Application Software: User interface

Fetching and Executing Instructions:
Fetching Steps

• The content of PC are placed on the address bus
• A Read signal is activated
• Data (instruction opcode) are read from RAM and placed on data bus
• The opcode is latched into the CPU’s IR
• The PC is incremented to prepare for the next fetch from memory

Executing Steps

• Decoding the opcode and generating the control signals to gate internal registers in and out the ALU and to signal ALU to perform the specified operation.

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Related topics:
Microcomputer System   |   Numbering System   |   Memory Basics   |   Digital Logic   |   ASCII Code   |   Computer Internals   |   ROM and RAM Memory

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List of topics: Microcomputer

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