8051 programming in c

Outline Types of programming languages

Machine language

Assembly language

High level language

Programming 8051 in C

Creating hex file using Keil Compiler

Burning hex file into microcontroller

ISP

Universal Super-pro programmer

Why program the 8051 in C?

It is easier and less time consuming 2 write in C than assembly

C is easier 2 modify & update

C code is portable

Toggle all the bits of P1 continuously

#include<reg51.h>

void main (void)

{

for(; ;) // repeat forever

{

P1=0x55; // 0x indicates data is in hex

P1=0xAA;

}

}

C data types for the 8051

Since one of the goals of 8051 C programmers is to create smaller hex files, it is worthwhile to re-examine C data types for 8051 C

This will help programmers 2 create smaller hex files

Unsigned char

8-bit data type-takes value in the range of 0-255 (00-FFH)

Most widely data types for the 8051

Signed char is default

Write an 8051 C program to send values 00-FF to P1

#include<reg51.h>

Void main (void)

{

unsigned char z;

for(z=0;z<=255;z++)

P1=z;

}

Signed char

8-bit data type dat uses d MBS-D7 to represent – or + value

Values from -128 to +127

Default is signed char

Unsigned int

16-bit data type

Values in the range 0-65535 (0000-FFFF H)

Used to set counter values of >256

Takes 2 bytes of memory

Sbit data type

Used for a single bit

Format:

sbit name= bit

For ex:

sbit LED =P1^0

Write an 8051 C program to toggle bit D0 of port P1 50,000 times

#include<reg51.h>sbit MYBIT=P1^0; //sbit is declared out of main

//programVoid main (void)

{unsigned int z;for(z=0;z<50000;z++){

MYBIT=o;MYBIT=1;

}}

Time delay using C

There are two ways to create a time delay in 8051 C:

1. Using a simple for loop

2. Using the 8051 timers

Three factors that can affect the accuracy of delay

Compiler choice

Crystal frequency

The 8051 design

Original 8051 design used 12 clock periods per m/c cycle

DS5000- 4 clock periods per m/c cycle

DS89C420- 1 clock periods per m/c cycle

Toggle all the bits of P1 continuously with some delay

#include<reg51.h>void main (void){

unsigned int x;for(; ;) // repeat forever{

P1=0x55; // 0x indicates data is in hexfor (x=0;x<40,000;x++); //delay size unknownP1=0xAA;for (x=0;x<40,000;x++);

}}

Get a byte of data from P0. If it is less than 100, send it to P1; otherwise send it to P2

#include<reg51.h>void main (void){

unsigned int mybyte;P0=0xFF;for(; ;) // repeat forever{

mybyte = P0; // 0x indicates data is in hexif(mybyte<100)

P1=mybyte; //send it to P1 if less than 100else

P2=mybyte; //send it to P2 if more than 100}

}