INTRODUCTION TO MICROPROCESSORS

MICROPROCESSORS INTRODUCTION

As manufacturers continue to pack more and more transistors onto a single chip, more and more of the stuff that was once "peripheral logic" has been integrated on the same chip as the CPU. A Microcontroller includes most or all the electronics needed in an embedded system in a single integrated circuit ("chip"). 

• CPU
• I/O ports
• RAM - contains temporary data
• ROM - contains program and constant data -- the firmware. Starting in 1993, many microcontrollers use Flash memory instead of true ROM to hold the firmware, but many engineers still refer to the Flash memory that holds the firmware as "ROM" to differentiate it from "RAM".
• Timers -- we discuss these later at Timers.
• Serial interface -- often a USART 
• EEPROM - contains "permanent" data
• Analog-to-digital converter
• Specialized functions

This list is roughly in order of integration. The earliest microcontrollers contained only the CPU and I/O ports; modern microprocessors typically contain the CPU, some I/O ports, and cache RAM; the cost of a micro-controller dropped dramatically once the CPU, I/O, RAM, and ROM could all be squeezed onto the same chip, because such a micro-controller no longer needs "address pins"; etc. The most highly integrated microcontrollers include all these parts on one chip.