DR. C. V. RAMAN UNIVERSITY

KARGI ROAD KOTA BILASPUR (C.G.)

2012-13

Microcontroller 8051&

Embedded System

Presentation On:

IntroductionEmbedded System(8051 Application)

Embedded System (8051 Application)

What is Embedded System?◦ An embedded system is closely

integrated with the main system◦ It may not interact directly with

the environment◦ For example – A microcomputer

in a car ignition control

An embedded product uses a microprocessor or microcontroller to do one task only

There is only one application software that is typically burned into ROM

Examples of Embedded Systems Keyboard Printer video game player MP3 music players Embedded memories to keep configuration

information Mobile phone units Domestic (home) appliances Data switches Automotive controls

MicrocontrollerA microcontroller (sometimes abbreviated µC, uC or MCU) is a small computer on a single integrated circuit containing a processor core, memory, and programmable input/output peripherals.

Microprocessor CPU is stand-alone, RAM,

ROM, I/O, timer are separate designer can decide on the

amount of ROM, RAM and I/O ports.

expansive versatility general-purpose

Microcontroller• CPU, RAM, ROM, I/O and

timer are all on a single chip• fix amount of on-chip ROM,

RAM, I/O ports• Highly bit addressable• for applications in which cost,

power and space are critical• single-purpose

Microprocessor vs. Microcontroller

8051 8052 `8031

RAM (bytes) 128 256128

ROM (kB) 4 4 0 I/O Ports 4 4 4 Timer 2 3 2 Interrupt Source 6 8 6 I/O Pins 32 32

32 Serial Port 1 1 1

* Also we have 8751 mcs in the series which is the UV-EPROM version of 8051 & AT89C51 is the one Atmel Fabrication Flash ROM version of 8051.

Comparison Between Microcontrollers Family:

Types of Microcontrollers

8051 Basic Component 4K bytes internal ROM 128 bytes internal RAM Four 8-bit I/O ports (P0 - P3). Two 16-bit timers/counters One serial interface

RAM

I/O Port Time

r

Serial COM Port

Microcontroller

CPU A single chip

ROM

Three formats are present in market1. DIP – Duel inline package

2. QFP –Quad flat package3. FBGA – Fine ball grid package

FBGA

QFP

DIP

Three criteria in Choosing a Microcontroller Meeting the computing needs of the task

efficiently and cost effectively◦ speed, the amount of ROM and RAM, the number of

I/O ports and timers, size, packaging, power consumption

◦ easy to upgrade◦ cost per unit

Availability of software development tools◦ assemblers, debuggers, C compilers, emulator,

simulator, technical support Wide availability and reliable sources of the

microcontrollers

Employs CISC, Harvard architecture An 8 - bit CPU 40 pin DIP package (40 - physical, 64 - logical) 4K On Chip ROM 128 bytes of On Chip user RAM 32 discrete I/O pins (4 groups of 8; individually accessed) Two 16 bit timers/counters Full duplex UART 6-Interrupts (5 vectored with 2 priority levels) Expandable up to max 64K of ROM Can support up to max 64K of EX-RAM Operating frequency is 24MHz-33MHz. +5V Regulated DC power supply is required to operate. RAM, ROM, I/O ports, one serial port and timers are all On-chip. Low-power Idle and Power-down Modes. 21 special function registers (SFRs). Crystal frequency of 11.0592MHz.

8051 Features

64K external code (program) memory (only read) PSEN

64K external data memory (can be read and write) by RD,WR

Code memory is selectable by EA (internal or external)

External Data & Code Memory

External code memory

ROM

D

74LS373

ALE

P0.0 P0.7

PSEN

A0 A7

D0 D7

P2.0 P2.7

A8 A15

OECS

EA

G

8051

RDWR

External data memory

8051 RAM

D

74LS373

ALE

P0.0 P0.7

PSEN

A0 A7

D0 D7

P2.0 P2.7

A8 A15

RDCS

EA

G

RDWR WR

8051 Foot Print

1234567891011121314151617181920

4039383736353433323130292827262524232221

P1.0P1.1P1.2P1.3P1.4P1.5P1.6P1.7RST

(RXD)P3.0(TXD)P3.1

(T0)P3.4(T1)P3.5

XTAL2XTAL1

GND

(INT0)P3.2(INT1)P3.3

(RD)P3.7(WR)P3.6

VccP0.0(AD0)P0.1(AD1)P0.2(AD2)P0.3(AD3)P0.4(AD4)P0.5(AD5)P0.6(AD6)P0.7(AD7)EA/VPPALE/PROGPSENP2.7(A15)P2.6(A14)P2.5(A13)P2.4(A12)P2.3(A11)P2.2(A10)P2.1(A9)P2.0(A8)

8051(8031)(8751)(8951)

Pin Description of the 8051 The 8051 is a 40

pin device, but out of these 40 pins, 32 are used for I/O.

24 of these are dual purpose, i.e. they can operate as I/O or a control line or as part of address or date bus.

IMPORTANT PINS (I/O Ports) 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

Port 1 （ pins 1-8 ） ： P1 （ P1.0 ～ P1.7 ）◦ Only 8-bit R/W - General Purpose I/O

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

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.

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

IMPORTANT PINS PSEN (out): Program Store Enable, the read

signal for external program memory (active low). ALE (out): Address Latch Enable, to latch

address outputs at Port0 and Port2 EA (in): External Access Enable, active low to

access external program memory locations 0 to 4K

RXD,TXD: UART pins for serial I/O on Port 3◦ XTAL1 & XTAL2: Crystal inputs for internal

oscillator. These 2 pins provide external clock.

◦Way 1 ： using a quartz crystal oscillator ◦Way 2 ： using a TTL oscillator

Pins of 8051 Vcc （ pin 40 ）：

◦Vcc provides supply voltage to the chip. ◦The voltage source is +5V.

GND （ pin 20 ）： ground RST （ pin 9 ）： reset

◦ input pin and active high （ normally low ） . The high pulse must be high at least 2

machine cycles.◦ power-on reset. Upon applying a high pulse to RST, the

microcontroller will reset and all values in registers will be lost.

Pins of 8051 /EA （ pin 31 ）： external access

◦There is no on-chip ROM in 8031 and 8032 .◦The /EA pin is connected to GND to indicate

the code is stored externally.◦/PSEN ＆ ALE are used for external ROM.◦For 8051, /EA pin is connected to Vcc.◦“/” means active low.

/PSEN （ pin 29 ）： program store enable◦This is an output pin and is connected to the

OE pin of the ROM.

Pins of 8051 ALE （ pin 30 ）： address latch enable

◦It is an output pin and is active high.◦8051 port 0 provides both address and data.◦The ALE pin is used for de-multiplexing the address

and data by connecting to the G pin of the 74LS373 latch.

Port 3 Alternate Functions

Microcontroller Architectures

CPUProgram + Data

Address Bus

Data Bus

Memory

Von NeumannArchitecture

CPUProgram

Address Bus

Data Bus

HarvardArchitecture

Memory

Data

Address Bus

Fetch Bus

0

0

0

2n

Block Diagram of 8051 MicrocontrollerOscillator and timing

4096 Bytes Program Memory

(ROM)

128 BytesData Memory

(RAM)

Two 16 Bit Timer/Event

Counters

8051 CPU

64 K Byte Bus Expansion

Control

Programmable I/O

Programmable Serial Port Full Duplex UART

Synchronous Shifter

Internal data bus

External interrupts

subsystem interrupts

Control Parallel portsAddress Data BusI/O pins

Serial InputSerial Output

Memory Space of 8051/8031

On-Chip MemoryInternal RAM

RAM memory space allocation in the 8051

7FH

30H

2FH

20H

1FH

17H

10H

0FH

07H

08H

18H

00HRegister Bank 0

(Stack )Register Bank 1

Register Bank 2

Register Bank 3

Bit-Addressable RAM

Scratch pad RAM

Bit Addressable RAM

Summary of the 8051 on-chip data memory(RAM)

DENOTION NAMES HEX

*A ACCUMULATOR E0*B ARITHMATIC REG. F0DPH ADDRESSING EXT. MEMORY(HIGH) 83DPL ADDRESSING EXT. MEMORY(LOW) 82*IE INTERRUPT ENABLE CONTROL A8*IP INTERRUPT PRIORITY B8

*P0 I/O PORT LATCH 80*P1 I/O PORT LATCH 90*P2 I/O PORT LATCH 8A*P3 I/O PORT LATCH 9A

PCON POWER CONTROL 87*PSW PROGRAM STATUS WORD D0

special function registers (SFRs)

*SCON SERIAL PORT CONTROL 98SBUF SERIAL DATA BUFFER 99

SP STACK POINTER 81

TMOD TIMER/COUNTER MODE CONTROL 8B *TCON TIMER/COUNTER CONTROL 89

TH0 TIMER O HIGH BYTE 8CTLO TIMER 0 LOWER BYTE 8ATH1 TIMER 1 HIGH BYTE 8DTL1 TIMER 1 LOWER BYTE 8B

> *= Bit addressable> Total No. Of SFRs =21 (11 are Bitwise & Bytewise )

(Remaining 10 are Bytewise only )

Register Banks Four banks of 8 byte-sized registers, R0 to R7 Addresses are :

18 - 1F for bank 310 - 17 for bank 208 - 0F for bank 100 - 07 for bank 0 (default)

Active bank selected by bits [ RS1, RS0 ] in PSW. Permits fast “context switching” in interrupt service routines (ISR).

Timer and CounterTMOD Register

TCON Register:

SCON (Serial CONtrol) register

These two bits of SCON register determine the framing of data by specifying the number of bits per character and start bit and stop bits.

There are 4 serial modes. SM0 SM1 0 0 Serial Mode 0 0 1 Serial Mode 1;(8 bit data, 1 stop bit, 1 start bit) 1 0 Serial Mode 2 1 1 Serial Mode 3

SM0, SM1

REN (Receive Enable) also referred as SCON.4. When it is High ,it allows the 8051 to receive data on the RxD pin.

So to receive and transfer data REN must be set to 1.

When REN=0,the receiver is disabled. This is achieved as below : SETB SCON.4 &

CLR SCON.4

REN, TI, RI

TI (Transmit interrupt) is the D1 bit of SCON register.When 8051 finishes the transfer of 8-bit character, it raises the TI flag to indicate that it is ready to transfer another byte.

RI (Receive interrupt) is the D0 bit of the SCON register.When the 8051 receives data serially ,via RxD, it gets rid of the start and stop bits and places the byte in the SBUF register. Then it raises the RI flag bit to indicate that a byte has been received and should be picked up before it is lost.

Contd…

An interrupt is an external or internal event that disturbs the microcontroller to inform it that a device needs its service.

8051 Interrupts

If two interrupt sources interrupt at the same time, then interrupt with the highest PRIORITY gets serviced first.

All interrupts have a power on default priority order. 1. External interrupt 0 (INT0)2. Timer interrupt0 (TF0)3. External interrupt 1 (INT1)4. Timer interrupt1 (TF1)5. Serial communication (RI+TI)

Interrupt Priorities

Interrupt

Global Interrupt Enable – must be set to 1 for any interrupt to be enabled

Interrupt enables for the 5 original 8051 interrupts:Timer 2

Serial (UART0)Timer 1

External 1Timer 0

External 01 = Enable0 = Disable

IP.7: reservedIP.6: reservedIP.5: Timer 2 interrupt priority bit )8052 only(IP.4: Serial port interrupt priority bitIP.3: Timer 1 interrupt priority bitIP.2: External interrupt 1 priority bitIP.1: Timer 0 interrupt priority bitIP.0: External interrupt 0 priority bit

Interrupt Priorities (IP) Register

--- PX0PT0PX1PT1PSPT2---

RS-232 interface (UART)Introduction: The RS-232 interface is the Electronic

Industries Association (EIA) standard for the interchange of serial binary data between two devices.

It was initially developed by the EIA to standardize the connection of computers with telephone line modems.

Three wires are sufficient: send data, receive data, and signal ground.

The remaining lines can be hardwired on or off permanently.

The signal transmission is:1. Bipolar2. Requiring two voltages(from 5 to 25 volts, of opposite polarity).

RS-232 stands for Recommended Standard. Serial communication devices are divided into

two types. Data Communication Equipment(DCE) Ex: modem, adapter Data Terminal Equipment(DTE) Ex: computer, terminal

Range & Specifications Maximum length of cable b/w TxD and

RxD should not exceed 100 feet.(One reason why the range of the RS-232-

C standard is limited is the need to charge and discharge the capacitance of the cable connecting the TxD and RxD.

The connector used is 25 pin connector with a specific arrangement of wires.

MAX232 (Level Convertor)* Usually, all

Digital ICs work on TTL or CMOS

voltage Level which can’t be

used to communicate over

RS232 protocol. So, a voltage convertor is

needed to convert such levels.* The most

commonly used RS-232 level convertor is

MAX232.* It consist two Tx

& Rx and is capable of Full

Duplex UART communication.

Interfacing to PC

Seven Segment Configurations

The most commonly used Seven segment display is Common Anode now days & suitable with 8051.

Code for Common AnodeSeven Segment Display

Seven segment Interfacing with 8051

Interfacingwith LCD

A LCD(2x16)(Liquid Crystal Diode) having 16pins and that are:1. 8 Data pins (D0-D7)2. 3 Control pins (RS, R/W, E)3. Supply pin (Vcc) & ground pin (GND)4. Contrast setting pin (VEE)5. LED+ & LED- pins

LCD contd..

Initialize LCD & wait/delay. Display ON, Cursor ON & wait. Clear LCD & wait. Shift cursor to the left & wait. Set cursor on Line1 or Line2 at the

position desired & wait. Send/Write the data LCD for display.

LCD Algorithms :

LCD Commands

Interfacingwith Keypad (4x4)

It is not part of the C language as such. Rather, it is a C language extension i.e. the subject of a technical report by the ISO working group named “Extensions for the Programming Language C to Support Embedded Processors”.

It Aims to provide portability and access to common performance ,increasing features of processors used in the domain of DSP, other electronics & embedded processing.

Embedded C

The hardware I/O extension is a portability feature of Embedded C. Its goal is to allow easy porting of device-driver code between systems.

KEIL software EMBEDDFD C(Using C51 cross compiler)

Key Words: To facilitate many of the features of the 8051.

C51 adds a number of new keywords to the scope of the language. The following is the list of keywordsAt sbit idatasfr bdata interruptsfr16bit largesmallcode taskdata - xdata

Embedded C contd..

Memory Areas: The 8051 architecture supports several physically separate memory areas or memory spaces for program and data.

There are memory spaces that may be:* INTERNAL DATA MEMORY* EXTERNAL DATA MEMORY* PROGRAM MEMORY

Embedded C contd..

1. Internal(a) data-1 byte space in internal RAM.(b) bdata-Bit addressable(c)idata-If data should be saved indirectly to the internal memory.

2. External(a) xdata-It uses dptr (16) register.(b) pdata-It uses R0,R1(8) register.

3. Program Memory(a) code-when have to access the code section of memory.

Embedded C contd..

Applications of Microcontrollers

Recent Wonders

Recent Wonders contd...

Its not an exaggeration if I say that ,today there is no electronic gadget on the earth which is designed without a Microcontroller. Ex: communication devices, digital entertainment, portable devices etc.

Conclusion:

Surabhi Vaishnav(7th Sem, ECE Discipline)

Presented by: