canolaokahumpkaΗλεκτρονική - Συσκευές

2 Νοε 2013 (πριν από 3 χρόνια και 8 μήνες)

68 εμφανίσεις

Micro controllers

A self
contained system in which a
processor, support, memory, and
input/output (I/O) are all contained in a
single package.

Types of Microcontrollers

Embeded (Self
contained) 8 bit

32 bit

Digital Signal Processors

Basic Features

Processor reset

Device clocking

Central processor

Program and Variable Memory (RAM)

I/O pins

Instruction cycle timers

More Sophisticated Features

in monitor/debugger program

Interrupt capability

Analog I/O (PWM and variable dc I/O

Serial I/O (synchronous, a synchronous)

Parallel I/O (including direct interface to a
master processor

External memory interface

Processor Architecture


Large amount of instructions each carrying out
a different permutation of the same operation

Functionality of the instructions is more
dependent upon the processor’s designer

Processor Architecture


Fundamental set of instructions

More control for users to design their
own operations

Processor Architecture

Princeton (Van Neumann) architecture

Common memory for program and data

Simple chip design

Execution of an instruction can take
multiple cycles

Processor Architecture

Harvard architecture

Separate memory space program and data

Instructions are executed in one cycle

Easier timing of loops and delays

Processor Architecture

Princeton architecture example

Mov acc, reg

Cycle 1

Read instruction

Cycle 2

Read data out of

Ram and put into


Processor Architecture

Harvard architecture example

Mov acc, reg

Cycle 1

Execute previous


Read “move acc, reg”

Cycle 2

Execute “move acc,



Microchip PIC

Micro controllers

(PIC 16F877)

Hardware Architecture

PIC Microcontrollers have following main

Harvard Architecture

RISC Feature

CPU pipelines instruction fetching and
execution in order to achieve an execution
of one instruction at every cycle

Memory Organization

Program Memory

Register File Memory

Program Memory

Used for storing compiled code

Each location is 14 bits long

Every instruction is coded as a 14 bit word

Addresses H’000’ and H’004’ are treated in
a special way

PC can address up to 8K addresses

Register File Memory

Consist of 2 Components

General Purpose Register (GPR) Files

Special Purpose Register (SPR) files

This portion of memory is separated into
banks of 128 bytes long

Register Addressing Modes

There are 3 types of addressing modes in

Immediate Addressing

Movlw H’0F’

Direct Addressing

Indirect Addressing

Direct Addressing

Uses 7 bits of 14 bit instruction to identify a
register file address


and 9

bit comes from RP0 and RP1 bits
of STATUS register.







Indirect Addressing

Full 8 bit register address is written the
special function register FSR

INDF is used to get the content of the
address pointed by FSR

Exp : A sample program to clear RAM
locations H’20’

H’2F’ .

Some CPU Registers






Instruction Set

Every Instruction is coded in a 14 bit word

Each instruction takes one cycle to execute

Only 35 instructions to learn (RISC)

Instruction Set

Uses 7 bits of 14 bit instruction to identify
register file address

For most instructions, W register is used as
a source register

The result of an operation can be stored
back to the W register or back to source

Some Arithmetic Operations

addwf FSR, w ; Add w to FSR and put

result in w

iorwf TMR0, f ; Inclusive OR w with

TMR0 and store result

in TMR0

addwf reg

; Add content of the reg

to content of the w and

store the result back

into reg (source)