Embedded systems, 8051 microcontroller

EMBEDDED SYSTEMS SUBMITTED TO: SUBMITTED BY: MR. ABISHEK SHARMA Arish Kumar Sharma 100640418019 ECE-A

What Are Embedded Systems? “Special purpose system which are either used as standalone or part of a big system” An Embedded System is one that has computer hardware with software embedded in it as one of its important components. An embedded product uses a microprocessor (or microcontroller) to do one task and one task only. A printer is an example of embedded system since the processor inside it performs only one task; namely, getting the data and printing it

WHERE ARE THEY PRESENT ? Household appliances Integrated systems in aircrafts and missiles Cellular telephones Electric and Electronic Motor controllers Engine controllers in automobiles Calculators Medical equipment’s Videogames Digital musical instruments

The necessary tools for a microprocessor/microcontroller  CPU: Central Processing Unit  I/O: Input /Output  Bus: Address bus & Data bus  Memory: RAM & ROM  Timer  Interrupt

Introduction to Microprocessors “A Microprocessor is a general purpose chip used to create multifunction device ” No RAM, ROM, I/O ports on CPU chip itself CPU is stand-alone, Must add RAM, ROM, I/O ports, and timers externally to make them functional Designer can decide on the amount of ROM, RAM and I/O ports Example ： Intel’s x86, Motorola’s 680x0

Introduction to Microcontrollers “A Microcontroller is a computer-on-a-chip optimized to control Electronic devices” CPU + I/O + Timer(s) [+ ROM] [+ RAM] All on single chip Limited RAM space, ROM space and I/O pins Low chip-count to implement a small system Low-cost at large quantities Development tools readily available at reasonable cost

Microprocessor System Contrasted With Microcontroller System

Microprocessor vs. Microcontroller Microcontroller Microprocessor • CPU, RAM, ROM, I/O and • CPU is stand-alone, RAM, timer are all on a single chip ROM, I/O, timer are separate • Fix amount of on-chip ROM, • Designer can decide the amount RAM, I/O ports of ROM, RAM and I/O ports • For applications in which cost, power and space are critical • Expansive • Not Expansive • Versatility • Single-purpose • General-purpose

Criteria for Choosing a Microcontroller Following must be kept in mind while choosing a microcontroller  Speed  Packaging  Power consumption  The amount of RAM and ROM on chip  The number of I/O pins and the timer on chip  How easy to upgrade to higher performance or lower power- consumption versions  Cost per unit

Microcontroller Architectures Memory 0 Address Bus Program CPU Data Bus + Data Von Neumann 2n Architecture Memory Address Bus 0 Program CPU Fetch Bus Harvard Address Bus 0 Architecture Data Bus Data

Features Of 8051 The Intel 8051 is used in embedded systems has  8-bit CPU  4k bytes ROM for the program  128 BYTES of RAM for variables  32 I/O lines ( 4 PORTS WITH 8 EACH )  2 timers  6 interrupt sources  Low cost per chip

8051 PIN description P1.0 1 40 Vcc P1.1 2 39 P0.0 (AD0) P1.2 3 P0.1 (AD1) 38 P1.3 4 37 P0.2 (AD2) P1.4 5 36 P0.3 (AD3) P1.5 6 35 P0.4 (AD4) P1.6 7 34 P0.5 (AD5) P1.7 8 8051 33 P0.6 (AD6) RST 9 32 P0.7 (AD7) (RXD) P3.0 10 31 EA/VPP (TXD) P3.1 11 30 ALE/PROG (INT0) P3.2 12 29 PSEN (INT1) P3.3 13 28 P2.7 (A15) (T0) P3.4 14 27 P2.6 (A14) (T1) P3.5 15 26 P2.5 (A13) (WR) P3.6 16 25 P2.4 (A12) (RD) P3.7 17 24 P2.3 (A11) XTAL2 18 23 P2.2 (A10) XTAL1 19 22 P2.1 (A9) GND 20 21 P2.0 (A8)

I/0 Ports:- 8051 microcontroller has four I/O ports P0, P1, P2 and P3 each use 8 pins making them 8 bit ports. All the ports can be used as either input or output •Port 0: Port 0 occupies a total of 8 pins (pins 32-39) .It can be used for input or output. To use the pins of port 0 as both input and output ports, each pin must be connected externally to a 10K ohm pull-up resistor. •Port 1: Port 1 occupies a total of 8 pins (pins 1-8). It can be used as input or output. In contrast to port 0, this port does not need any pull-up resistors since it already has pull-up resistors internally. •Port 2 : Port 2 occupies a total of 8 pins (pins 21- 28). It can be used as input or output. Just like P1, P2 does not need any pull-up resistors since it already has pull-up resistors internally. •Port 3 : Port 3 occupies a total of 8 pins (pins 10 -17). It can be used as input or output. P3 does not need any pull-up resistors, the same as P1 and P2 did not. Port 3 has the additional function of providing some extremely important signals such as interrupts, etc.

IMPORTANT PINS  VCC (Pin-40): Vcc provides supply voltage to the chip. The voltage source is +5V.  GND (Pin-20): It is ground pin.  RST (Pin-9): It is reset pin. Upon applying high pulse to this pin the micro controller will reset and terminate all activities.  XTAL1 & XTAL2 (Pin-18,19): These 2 pins provide external clock using a quartz crystal oscillator Crystal inputs for internal oscillator.  PSEN (Pin-29): Program Store Enable, the read signal for external program memory.

IMPORTANT PINS ALE (Pin-30): Address Latch Enable, to latch address outputs at Port0 and Port2, used for both data and address transmission. EA (Pin-31): External Access pin should be connected to Vcc in order to fetch code from internal program memory and to fetch code from external program memory EA is connected to Ground. Interrupts (Pin-12,13): An interrupt is an event that disturbs the microcontroller to inform it that a device needs its service. Timers/Counters (Pin-14,15): They are used for counting internal or external events.

TIMER/COUNTERS IN 8051 TI MER 8051 is of two types  Timer T0 16-bit  Timer T1 16-bit Features • Both Timer T0 and T1 are 16 bits wide. • When used as a “timer” the register is programmed to count internal clock pulses • When used as a “counter” the register is programmed to count external clock pulses

INTERRUPT Interrupt is an event that causes program to change its normal execution and branch up to specific subroutine putting normal program on hold.  Whenever any device needs its service, the device notifies the microcontroller by sending it an interrupt signal.  Upon receiving an interrupt signal, the microcontroller interrupts whatever it is doing and serves the device.

ADDRESSING MODES Different addressing modes in 8051 microcontroller are •IMMEDIATE ADDRESSING •REGISTER ADDRESSING •DIRECT ADDRESSING •REGISTER INDIRECT ADDRESSING

Immediate Addressing : This addressing mode is named as “immediate” because it transfers an data immediately to the destination operand. For example - •MOV A, #77H ; Loads 77 (hexadecimal) to A and stores in A •ADD A, #4DH ; Adds 4D (hexadecimal) to A and stores in A •MOV DPTR, #1234H ; Moves 1234 (hexadecimal) to data pointer The ‘#’ symbol before 77H indicates that operand is a data (8 bit). If ‘#’ is not present then the hexadecimal number would be taken as address Register Addressing : Used while moving data between two registers. Moving data between two Rn registers is not allowed. For example- •ADD A, R0 ;Adds content of R0 to A and stores in A •MOV A, R1 ;Copy contents of R1 into A

Direct Addressing : There are 128 bytes of RAM in 8051 and have been assigned addresses 00 to 7FH. Entire 128 bytes of RAM can be accessed by using direct addressing mode. For example - •MOV R0, 088H; Save the contents of RAM location 88h to R0 Register Indirect Addressing : An address is considered to be the address of an address, rather than the address of a value. For example - •MOV A, @R0; Moves content of address pointed by R0 to A Value inside R0 is considered as an address, which holds the data to be transferred to Accumulator.

SYSTEMS AND APPLICATIONS Embedded systems are more than part of human life. For instance, one cannot imagine life without mobile phones for personal communication. Its presence is virtually unavoidable in almost all facets of human endeavor. We can clearly identify the trend as to where the future of embedded systems is heading. Conventionally, chip manufacturers developed faster single core processors to meet the ever increasing performance requirements but soon they realized that increasing frequency, though offered certain benefits had drawbacks too such as: • It drove to higher power consumption • Overall cost increased as the peripherals surrounding also needed to operate at matching speed, which was truly not practical in all cases, there by driving the costs. So semiconductor manufacturers recognized that the way forward is to build processors that run at lower frequency and voltages but include parallel cores onto single chip. The overall performance increases because multicores can perform more than one task at given point of time, so today most of our devices such as smartphones, are indeed getting 'smarter‘ and ‘smaller’

Embedded operating systems Traditionally embedded systems did away with an operating system (OS), it had lightweight control program/monitor to offer limited I/O and memory services, however, as the systems became complex, it was inevitable to have OS which offered low latency real-time response. Most of the new designs today are moving away from proprietary OS and tool chains and are more and more opting for open source platforms both of development and deployment as the key market differentiator for them is cost. Royalty free licensing deployment is the key for reducing the end user costs so OS like Linux embedded and new OS such as Android are making inroads into places where traditionally Windows CE/Vx works etc., used to play. Today many new handhelds and smart phones are embracing Android. Convergence embedded systems and applications The retail segment is one of the fastest growing segments in emerging markets and the trend in retail markets is moving towards improving the user experience, which is most certainly setting trend towards increased performance, connectivity and rich graphics, while reducing power consumption and size of the device. Ultrabook is a latest example which aims in reducing size of conventional laptops, while efficiently managing power consumption and also improving performance

Healthcare Electronic medical devices and other technological innovations with the convergence of biotech, nanotech, manufacturing tech making breathtaking transformations in healthcare delivery and creating new health care paradigms. The fastest growing markets within medical for semiconductors are home monitoring and diagnostic device ECG, pulse rate, temperature, oxygen, blood pressure etc. Embedded digital security and surveillance In the ever increasing interconnected world, Digital embedded security is no more an option but a necessity as it is very critical for more transactions happening over embedded devices as front ends. Digital security and surveillance is currently in the host of new applications in the embedded arena which is benefiting from multicore phenomenon. The applications based on computer vision and tracking offers multiple benefits in capturing, post processing and identification and alerting of security video in real time. Telecommunications If ever there is an industry that has reaped the benefits to Embedded Technology, for sure, it is only Telecommunications. The Telecom industry utilizes numerous embedded systems from telephone switches for the network to mobile phones at the end-user.

Automotive With drive across the world to improve on emission controls and bring in efficiency in usage of fossil fuels, the automotive segment is challenged by various factors and embedded systems are clearly the ways and means of achieving multiple objectives in this segment taking it from infotainment systems, engine control unit, Car-area-network, fuel management, safety systems all need embedded to be in it. Entertainment While we have seen mobiles, handhelds, iPods etc., have changed the landscape of the personal entertainment in the world in the recent past, the emerging trend is adding more intelligence in the personal entertainment, communication devices by converging the social networks, city information, location based services into a single device. Smart cards industry Smart cards, though began prominently as either a debit or a credit card, are now being introduced in personal identification and entitlement schemes at regional, national, and international levels. Smart cards are appearing now as Citizen Cards, drivers’ licenses, and patient cards.

Embedded systems, 8051 microcontroller

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