HOW a Computer Works ? Anatomy of Microprocessor

Microprocessor Millions of super-fast transistor switches control streams of binary data

CPU (Central Processing Unit) CPU runs Program Stored in Memory –typically RAM or ROM

Structure of Memory Memory stores Instructions and Data in an array of registers that can be accessed by a unique address value.

Binary (Machine) Instructions Instruction Structure Architecture (ISA) – User’s view of Microprocessor

Assembly Code Programming Language (Code) provides the required Algorithm: Assembly - low level C - higher level

Control Unit and ALU Digital Systems split into Data Path and Control Path

Data Registers ALU result stored in a Register (sometimes called Accumulator). Registers are controlled by the Set and Enable Signals from CU.

CPU System Bus CPU Registers belong to Data Path. They are attached to the CPU System Bus.

Registers Latch Data Data on Data Bus is changing fast. Registers hold the values captured at different times.

Instruction register (IR) At times System Bus carries Instructions... they are captured in IR for use by CU ↑ IR

Flags Register Flags: Zero (ZF), Carry (CF), Overflow (OV), Sign (SF) etc Flags Register stores the status following ALU operation:

Program Counter (PC) ↑ PC Program Counter holds the memory address of the current instruction

Memory Address Register (MAR) ↑ MAR MAR holds the memory address of the data to be fetched.

Conditional Instructions Conditional instructions provide the algorithmic Flow Control

Ports ↑ Interface to External World A Port normally involves a group of registers holding data and port configuration

Microprocessor Pins There is always shortage of pins, so some have multiple (configurable) options.

Motherboard

Non-volatile Storage Non-volatile memory keeps data even if power is off. Examples: ROM or FLASH ROM.

Hard Drive (HD) Hard Drive is a non-volatile storage medium. Unlike random addressable memory, HD uses data formatting so the processor cannot run any code stored on HD directly from there.

Computer System Microprocessor = CPU on a single IC chip Microcontroller = CPU + MEMORY + PORTS on a single IC chip