Introduction to Embedded system programming using 8051

1. DR. VIKAS J. DONGRE
HOD ELECTRONICS & TELECOM
GOVERNMENT POLYTECHNIC WASHIM (MS)
EMAIL: DONGREVJ1@GMAIL.COM
 Unsigned char
 Signed char
 Unsigned int
 Signed int
 Sbit (SFR bit)
 Bit
 sfr

2. Microcontroller 8051 Assembly language
programming
 Need to know architecture
 Need to know all SFRs
 Need to know various registers, register banks
 Need to know various instructions
A
B
R0
R1
R2
R3
R4
R5
R6
R7

5. ORG 0000H
START:
MOV P2,#0FFH
CALL DELAY
MOV P2,#00H
CALL DELAY
SJMP START
DELAY:
MOV R2,#01H
D2:
MOV R1,#0E1H
D1:
MOV R0,#0FFH
D0: DJNZ R0,D0
DJNZ R1,D1
DJNZ R2,D2
RET
END
Microcontroller 8051 Assembly language programming

6. The reasons for writing programs in C
 It is easier and less time consuming to write in C than Assembly
 C is easier to modify and update
 C supports I/O
 You can use code available in function libraries
 One doesn't need to remember all architecture, registers,
instructions of specific microcontroller
 C code is portable to other microcontroller with little of no
modification
 A good understanding of C data types for 8051 can help
programmers to create smaller hex files

7. Comparison of Assembly language and Embedded C
Assembly program Embedded C program
1. Program executes faster Program executes slower
2. Hard to develop and maintain Easy to develop and maintain
3.Requires less memory Requires huge memory
4.Not portable as machine dependent Portable as machine independent
6. Higher software development cost Less software development cost
7.Less scalable and reliable More scalable and reliable
5. Size of program is less Size of program is largs

8. Supported data types in embedded C
 Unsigned char
 Signed char
 Unsigned int
 Signed int
 Sbit (single bit)
 Bit
 sfr

9. Data types and their ranges
Data types Size Range
bit 1-bit RAM bit-addressable only
sbit 1-bit SFR bit-addressable only
(signed) int 16-bit -32768 to +32767
unsigned int 16-bit 0 to 65535
(signed) char 8-bit -128 to +127
unsigned char 8-bit 0 to 255
Sfr 8-bit 0 to 255
C compilers use the signed char as the default if we do not put the
keyword unsigned

10. Write an 8051 C program to send values 00 – FF
to port P1.
#include <reg51.h>
void main(void)
{
unsigned char z;
for (z=0;z<=255;z++)
P1=z;
}
Solution:

11. Write an 8051 C program to send hex values for ASCII
characters of 0, 1, 2, 3, 4, 5, A, B, C, and D to port P1.
Solution:
#include <reg51.h>
void main(void)
{
unsigned char
mynum[]={'0','1','2','3','4',’5’6',
'7‘,’8','9','A'};
unsigned char z;
for (z=0;z<=10;z++)
P1=mynum[z];
}

12. Write an 8051 C program to toggle all the bits of P1
continuously.
Solution:
//Toggle P1 forever
#include <reg51.h>
void main(void)
{
for (;;)
{
P1=0x55;
P1=0xAA;
}
}

13. Write an 8051 C program to toggle bit D0 of the
port P1 (P1.0) 50,000 times.
Solution:
#include <reg51.h>
sbit MYBIT=P1^0;
void main(void)
{
unsigned int z;
for (z=0;z<=50000;z++)
{
MYBIT=0;
MYBIT=1;
}
}