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DEPARTMENT OF

ELECTRONICS &COMMUNICATION

SUBMITTED TO: - SUBMITTED BY:SUBMITTED BY:--

Mr. MANISH SAXENA MANOHAR KUMAR

0112EC071051

Presentation in

MICROCONTROLLER

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8051 is made by Intel. It is one of the most widely

used microcontroller in the world. A stand alone, high performance, single chip

computer for

control applications.

Small, cheap and 40 pins.

64K program memory. 64K data memory.

Microcontroller- Intel 8051

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Wednesday, November 17,2010

Feature 8051 8052 8031

ROM (program space in bytes) 4K 8K 0K

RAM (bytes) 128 256 128

Timers 2 3 2

I/O pins 32 32 32

Serial port 1 1 1

Interrupt sources 6 8 6

Comparison of the 8051Family Members

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Block Diagram

CPU

On-chip

RAM

On-chip

ROM for

program

code

4 I/O Ports

Timer 0

Serial

PortOSC

Interrupt

Control

External interrupts

Timer 1

Timer/Counter

Bus

Control

TxD RxDP0 P1 P2 P3

Address/Data

Counter

Inputs

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8051 Architecture

8051 architecture contains the following:8 bit CPU with registers A and B

16 bit program counter(PC) and data pointer(DPTR)

8 bit program status word(PSW)

8 bit stack pointer

Internal ROM of 0(8031) to 4K(8051)

Internal RAM of 128 Bytes4 register banks 00-1f

16 bytes(bit addressable) 20-2f

80 bytes of general purpose data memory 30-7f 32 I/O pins

arranged as four 8 bit ports (P0 P3)

2 16-bit timer/counters: T0 and T1

Full duplex serial data receiver/transmitter:

Control registers: TCON, TMOD, SCON, PCON, IP

and IE

2 external and 3 internal interrupt sources

Oscillator and clock circuits

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8051 CPU RegistersA (Accumulator)B

PSW (Program Status Word)

SP (Stack Pointer)

PC (Program Counter)

DPTR (Data Pointer)

Used in assembler

instructions

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Mahdi Hassanpour

8051Flag bits and the PSW register PSW Register

CY AC F0 RS1 OVRS0 P--

CYPSW.7Carry flagACPSW.6Auxiliary carry flag--PSW.5Available to the user for general purpose

RS1PSW.4Register Bankselector bit 1RS0PSW.3Register Bankselector bit 0

OVPSW.2Overflow flag--PSW.1User define bitPPSW.0Parity flag Set/Reset odd/even parity

RS1 RS0 Register Bank Address

0 0 0 00H-07H

0 1 1 08H-0FH

1 0 2 10H-17H

1 1 3 18H-1FH

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Pins of I/O Port

The 8051 has four I/O ports

Port 0pins 32-39P0P0.0P0.7

Port 1pins 1-8 P1P1.0P1.7

Port 2pins 21-28P2P2.0P2.7 Port 3pins 10-17P3P3.0P3.7

Each port has 8 pins.

Named P0.XX=0,1,...,7, P1.X, P2.X, P3.X

Ex

P0.0 is the bit 0

LSB

of P0 ExP0.7 is the bit 7MSBof P0

These 8 bits form a byte.

Each port can be used as input or output (bi-direction).

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Port Operations

Port 0 may serve as inputs, outputs, or as a low

Order address and data bus for external memory.

Port 1 may be used as input/output port.

Port 2 may be used as input/output or high order

address byte.

Port 3 may be used as an input/output and for

Some alternate function.

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Prof. Cherrice Traver ECE/CS-352: Embedded MicrocontrollerSystems

System Clock Generator

Input

circuit

8051

sysclk

Original 8051 uses 12 sysclk cycles per machine cycle

External crystal oscillator

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Serial Port (UART)

SerialPort

TX (transmit)

RX (receive)

Data sent and received serially

BAUD rate must agree between sender and receiver

Transmission modes selected using SFR

Original 8051 had one serial port

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Registers

0706050403020100

R7R6R5R4R3R2R1R0

0F

08

17

10

1F

18

Bank 3

Bank 2

Bank 1

Bank 0

Four Register BanksEach bank has R0-R7

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Special Function Registers

DATA registers

CONTROL registers

TimersSerial ports

Interrupt system

Analog to Digital converter

Digital to Analog converter

Etc.

Addresses 80h FFh

Direct Addressing used to access

SPRs

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Interrupts

Interrupts are just special subroutines that may (or may

not) be called explicitly.If conditions are right, when an interrupt occurs, then the

processor will stop what it is doing, and jump to a specific

place in memory (decided by the Intel 8051 designers)

hooked by that particular interrupt.

It is up to the programmer to make sure that you supply a

sensible further course of action. This is called theinterrupt handler routine or interrupt service routine.

Interrupt programming

Signals or conditions generated external to the main

program

External events such as a change in a logic value

Overflow of a counter Arrival of data at the serial port.

Interrupts can be enabled or disabled by the programmer.

(Although some interrupts are non- maskable.)

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Interrupt Control

Original 8051 has five sources of interrupts

Timer 1 overflow

Timer 2 overflow

External Interrupt 0

External Interrupt 1 Serial Port events (buffer full, buffee empty, etc)

Interrupts enabled and disabled using SFR

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Timers andCounters

The 8051 comes equipped with two timers, both

of which may be controlled, set, read, andconfigured individually. The 8051 timers have

three general functions:

1) Keeping time or calculating the amount of

time between events,

2) Counting the events themselves, or3) Generating baud rates for the serial port. Could use

software techniques, but this keeps the

processor occupied. Better to use interrupts & the

two 16- bit count- up timers. Can either be

programmed to:

1. count internal - acting as timer

2. count external - acting as counter

All counter action is controlled by the TMOD

(timer mode register) and the TCON (timer/counter control re ister .

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Internal TimersOriginal 8051 has 2 timers

16 bits

TH0 : TL0

Timer 0

16 bits

TH1 : TL1

Timer 1

Timers increment on each system clock

Timer registers (TH0, TL0, TH1, TL1) can be read or written to

Timer overflow can cause interrupts or set SFR bits high

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Timers and Counters

Applications: (counter)

Say we want to count a specified number of events (clock

pulses or external events), then

1.Store the start number in the counter. (Value maxcount

desired count+ 1)

2. Counter automatically increments (in the background)

3. When it rolls over to zero, it will set the timer flag.

4. Test the flag in the program, or generate an interrupt

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Applications: (Timer)

Timing configures the counter to count the internal clock

frequency/ 12. (E. g. if fc = 6:0Mhz, then the timer clockwill have a frequency of 500kHz.)

To configure as a timer:

1. Clear C/T~ bit in TMOD (Count internal frequency)

2. Set TRx in the TCON (timer run) and the gate bit in the

TMOD must be 0, or the externalpin INTx~ must be 1.

3. Select one of 4 modes.

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