2. Contents
• Introduction
• Feature of 8051
• Microcontroller Vs Microprocessor
• Internal Architecture 8051
• Pin Diagram of 8051
• Memory Organization of 8051
Prof. R. S. Devhade (LKDKB Science College, Lonar)

3. Introduction
Prof. R. S. Devhade (LKDKB Science College, Lonar)
• The microcontroller is nothing but the small programmable controller and same as
that of single chip computer.
• A microcontroller is a computer present in a single integrated circuit which is
dedicated to perform one task and execute one specific application.
• It contains memory, programmable input/output peripherals as well a processor.
• Microcontrollers are mostly designed for embedded applications and are heavily
used in automatically controlled electronic devices such as cell phones, cameras,
microwave ovens, washing machines, etc.
• Microcontrollers are used to execute a single task within an application.
• It consists of CPU, RAM, ROM, I/O ports, serial port, Timers, ADC & DAC, Interrupt
control, Special function block etc.
• All of these above blocks are built in a single chip of 40-pin for 8051 µc.

4. • The Intel 8051is belonging to MCS51 family which is 8-bit µc family have the
different members as 8031, 8048,8051,8751 out of these 8-bits µc has inbuilt E-
PROM available in it.
•
• The 8051 Microcontroller is one of the basic types of microcontroller, designed by
Intel in 1980’s.
• This microcontroller was based on Harvard Architecture and developed primarily for
use in embedded systems technology.
• Normally, this microcontroller was developed using NMOS technology, which
requires more power to operate.
Prof. R. S. Devhade (LKDKB Science College, Lonar)

5. Feature of 8051
• Microcontroller having inbuilt 4KB of ROM and 128 byte RAM. The ROM is also
called program memory where as RAM is called as data memory.
• Microcontroller having four I/O ports each of 8-builts available as P0, P1, P2 & P3.
All these port are bit addressable.
• It is having Boolean processor inbuilt available which operates on various Boolean
instruction.
• The microcontroller has five inbuilt interrupt source, out of which two are hardware
and remaining three are software interrupt.
• It has inbuilt 8-bit of data bus and 16-address bus.
• It has 64KB attached external memory because of 16-bit address bus.
• It has four register banks as bank0, bank1, bank2, bank3; each bank is of 8-byte
containing 8 register each of single byte (8-bit).
• It has two 16-bit timer and counter. Prof. R. S. Devhade (LKDKB Science College, Lonar)

6. Microprocessor Vs Microcontroller
It is a single chip without I/O, memory,
timer/counter and serial interface
It is single chip with built inside ports,
timer/counter, memory and serial interface.
The instruction of microprocessor is lengthy. The instruction set of microcontroller is small.
Microprocessor have not bit addressable
instruction
Microcontroller has built bit addressable
instruction.
Program of microprocessor generally terminated
with HLT instruction.
Program of microcontroller generally terminated
with RET instruction.
Microprocessor is not operated with Boolean
instructions.
Microcontroller operated with Boolean
instruction.
Microprocessor have not inbuilt RAM or ROM Microcontroller have inbuilt internal RAM or
ROM.
Very few pins are programmable. Most of the pins are programmable.
Microprocessor have not inbuilt I/O port Microcontroller have inbuilt I/O four port.
Various microprocessor are 8085, 8086 Various microcontroller are 8031, 8051.
Prof. R. S. Devhade (LKDKB Science College, Lonar)

7. Internal Architecture of 8051
Prof. R. S. Devhade (LKDKB Science College, Lonar)

8. • Accumulator
• Register B
• 8-bit ALU
• PSW or flag register (8-bit)
• PC (16-bit)
• DPTR (16-bit)
• SP (8-bit)
• Four I/O port
• Various SFR
The above figure shows the block diagram of Intel 8051 µc. it contains
the following important block:
Prof. R. S. Devhade (LKDKB Science College, Lonar)

9. Pin Diagram of 8051
Prof. R. S. Devhade (LKDKB Science College, Lonar)

10. • One of the most useful features of the 8051 is that it contains four
I/O ports (P0 - P3)
• Port 0 （pins 32-39）：P0（P0.0～P0.7）
– 8-bit R/W - General Purpose I/O
– Or acts as a multiplexed low byte address and data bus for external memory
design
– The default address of these pin is 80H
• Port 1 （pins 1-8） ：P1（P1.0～P1.7）
– Only 8-bit R/W - General Purpose I/O
– The default address of these pin is 90H
• Port 2 （pins 21-28）：P2（P2.0～P2.7）
– 8-bit R/W - General Purpose I/O
– Or high byte of the address bus for external memory design
– The default address of these pin is A0H
• Port 3 （pins 10-17）：P3（P3.0～P3.7）
– General Purpose I/O
– if not using any of the internal peripherals (timers) or external interrupts.
– The default address of these pin is B0H
• Each port can be used as input or output (bi-direction)
IMPORTANT PINS (IO Ports)
Prof. R. S. Devhade (LKDKB Science College, Lonar)

11. Memory Organization of 8051
 An 8051 microcontroller is having two types of memory organized as
• Internal memory
• External memory
 The memory structure or organization for 8051 is follows
Prof. R. S. Devhade (LKDKB Science College, Lonar)

12. • The internal Memory of 8051 Microcontroller is separated in Program Memory (ROM)
and Data Memory (RAM).
• The Program Memory of the 8051 Microcontroller is used for storing the program to be
executed i.e. instructions.
• The Data Memory on the other hand, is used for storing temporary variable data and
intermediate results.
• The ROM of 8051 is also called as
program memory which is inbuilt in
microcontroller.
• The starting address of this memory
will be from 000H, ending up to
FFFH.
 4 KB ROM:
Prof. R. S. Devhade (LKDKB Science College, Lonar)

13. Program memory accessed through EA pin. In program memory two
categories takes place:
If EA is HIGH, internal program memory is
accessed from 0000H to 0FFFH memory
location and external program memory
accessed from 1000H to FFFFH memory
locations.
If EA is LOW, only external program
memory accessed from 0000H to FFFFH
memory locations.
Prof. R. S. Devhade (LKDKB Science College, Lonar)

14.  128 byte RAM:
 This memory is also called as data memory.
 The 128 byte RAM (data memory) which is further distributed as:
• 32-byte register bank
• 16-byte bit addressable
• 80-byte scratched pad

15. • Also an external memory of size maximum up to 64KB
can be integrated with 8051 microcontroller.
• The 8081 microcontroller has 16 address lines, hence
the total memory addressing capacity is
216 = 64KB.
• Intel 8051 can be interface with maximum 64KB of
memory.
• The starting address to this memory is from 0000H to
FFFFH.
Prof. R. S. Devhade (LKDKB Science College, Lonar)

16. THANK
YOU……