MECVE 104EMBEDDED SYSTEM HARDWARE

ARCHITECTURE I

By

AJAL.A.J

AP/ ECE DEPARTMENT MAIL: ec2reach@gmail.comMob: 8907305642

Basics of computer architecture and binary number systems.

Introduction to Embedded Systems-

Application domain, Features and General characteristics of embedded systems,

http://www.esacademy.com/assets/faqs/primer/2.htm

Microprocessor vs microcontroller

Both embedded processors and microcontrollers perform controlling functions inside a computer system.

The Difference Between an Embedded Processor & a Microcontroller

• Controllers Controllers are special pieces of digital

equipment that control some aspect of their environment, according to responses from that environment. Typical types of controllers include those for home temperature regulation systems or security systems. A controller can be thought of as a self-contained computer that controls another system. Often, older controllers were large pieces of machinery contained externally from the system they controlled.

Microcontrollers

• As computer miniaturization progressed through the mid to late 1900s, controllers became smaller and smaller. All the parts of a controller, including memory and I/O devices, became integrated with the controller as a standard. Finally, when the entire controller apparatus was able to fit on single chips, they became known as "microcontrollers." A microcontroller contains everything required to control an external system, and nothing else. This limiting of microcontroller functionality to the basic requirements of a control unit makes implementing microcontrollers cheap and easy.

Embedded Processors

• An "embedded" processor is simply a computing device placed inside a system it controls. A processor embedded into a system handles all the computation and logical operation of a computer. The embedded processor also handles such tasks as storing and retrieving data from memory, and processing data from any inputs or outputs. Embedded processors often work as part of a computer system, alongside memory and I/O devices.

Differences• The primary difference between microntrollers and

embedded processors is makeup and integration. Embedded processors, while in a sense "controlling" the system they are a part of, require external resources such as RAM and registers in order to do so.

• A processor is not a control "system." • Microcontrollers, on the other hand, contain everything

required to control a system in a single chip. A microcontroller might contain an embedded processor as part of its makeup, but also combines other computer parts, such as memory and signal registers, in a single chip.

microcontrollers

Memory architecture of microcontroller are two types, they are namely:1. Harvard memory architecture microcontroller2. Princeton memory architecture microcontroller

1. Harvard Memory Architecture Microcontroller:

• The point when a microcontroller unit has a dissimilar memory address space for the program and data memory, the microcontroller has Harvard memory architecture in the processor.

2. Princeton Memory Architecture Microcontroller:

• The point when a microcontroller has a common memory address for the program memory and data memory, the microcontroller has Princeton memory architecture in the processor.

Classification of MCUs.

4 Types of Microcontrollers

1.Microcontroller 8051

2.Renesas Microcontroller

3.AVR Microcontrollers

4.PIC Microcontroller

1. Microcontroller 8051

2. Renesas Microcontroller

Renesas offers the most versatile microcontroller families in the world

Renesas is latest automotive microcontroller family that offers high performance feature with exceptionally low power consumption

Features and Benefits of the RX Microcontrollers

1. Low power consumption is realized using multi-core technology

2. Support for 5V operation for industrial and appliance designs

3. Scalability from 48 to 145 pins and from 32KB to 1MB flash memory, with 8KB of data flash memory included

4. Integrated safety feature5. An integrated rich function set of 7 UART, I2C, 8 SPI,

comparators, 12-bit ADC, 10-bit DAC and 24-bit ADC (RX21A), which will reduce system cost by integrating most functions

Application of Renesas Microcontroller:

1. Industrial automation

2. Communication applications

3. Motor control applications

4. Test and measurement

5. Medical applications

3. AVR Microcontrollers

• AVR microcontroller is developed by Alf-Egil Bogen and Vegard Wollan from Atmel Corporation. The AVR microcontrollers are modified harvard RISC architecture with separate memories for data and program and speed of AVR is high when compare to 8051 and PIC.

The AVR is stands for Alf-Egil Bogen and

Vegard Wollan’s RISC processor.

3. AVR Microcontrollers

It comes in 28 pin DIP

Features of AVR Microcontroller:

1. 16KB of In-System Programmable Flash2. 512B of In-System Programmable EEPROM3. 16-bit Timer with extra features4. Multiple internal oscillators5. Internal, self-programmable instruction flash memory up to 256K6. In-system programmable using ISP, JTAG or high voltage methods7. Optional boot code section with independent lock bits for protection8. Synchronous/asynchronous serial peripherals (UART/USART)9. Serial peripheral interface bus (SPI)10. Universal serial interface (USI) for two/three-wire synchronous data transfer11. Watchdog timer (WDT)12. Multiple power-saving sleep modes13. 10-bit A/D Converters, with multiplex of up to 16 channels14. CAN and USB controller support15. Low-voltage devices operating down to 1.8v

Difference between 8051 and AVR Controllers:

1. 8051s are 8-bit controllers based on CISC architecture, AVRs are 8-bit controllers based on RISC architecture

2. 8051 consumes more power than AVR microcontroller

3. In 8051, we can program easily than the AVR microcontroller

4. The speed of AVR is more than the 8051 microcontroller

Classification of AVR Controllers:

AVR Microcontrollers are classified into three types:• TinyAVR – Less memory, small size, suitable only for

simpler applications• MegaAVR – These are the most popular ones having

good amount of memory (up to 256 KB), higher number of inbuilt peripherals and suitable for moderate to complex applications

• XmegaAVR – Used commercially for complex applications, which require large program memory and high speed

Features of ATmega328:

1. 28-pin AVR microcontroller2. Flash program memory of 32kbytes3. EEPROM data memory of 1kbytes4. SRAM data memory of 2kbytes5. I/O pins are 236. Two 8-bit timers7. A/D converter8. Six channel PWM9. In built USART10. External Oscillator: up to 20MHz

Typical Circuit of AVR Microcontroller:

Applications of AVR Microcontroller:

• There are many applications of AVR microcontroller; they are used in home automation, touch screen, automobiles, medical devices and defense.

4. PIC Microcontroller

A Typical Application Circuit of PIC16F877A

Advantages of PIC:

• It is a RISC design• Its code is extremely efficient, allowing the PIC

to run with typically less program memory than its larger competitors

• It is low cost, high clock speed

CISC vs RISC

Classification According to Instruction Set

CISC vs RISC• CISC: CISC is a Complex Instruction Set Computer.

It allows the programmer to use one instruction in place of many simpler instructions.

• RISC: The RISC is stands for Reduced Instruction set Computer, this type of instruction sets reduces the design of microprocessor for industry standards. It allows each instruction to operate on any register or use any addressing mode and simultaneous access of program and data.

Figure of meritsA figure of merit is a quantity used to

characterize the performance of a device, system or method, relative to its

alternatives. In engineering, figures of merit are used as a marketing tool to

convince consumers to choose a particular brand.

a numerical quantity based on one or more characteristics of a system or device that represents a measure of efficiency or effectiveness. A FOM may be either a qualitative or quantitative measure, depending on the accuracy and integrity of the data used to calculate the FOM.

@ Modulation Systems

• In modulation systems for communication, figure of merit of a device means the ratio of output Signal to Noise Ratio to the input Signal to Noise Ratio.

@ Amplitude modulation

• Figure of merit for Amplitude modulation is given by

• Figure of merit for DSB-SC receiver or that of an SSB modulation is always unity. Therefore noise performance of AM receiver is inferior to that of a DSB-SC receiver or an SSB receiver.

@ Frequency modulation

• Figure of merit for Frequency modulation is given by

Embedded systems:

The hardware point of view• MCU,• memory, • low power design,• pull up and pull down resistors .• Sensors,• ADCs and• actuators .

Pull up and Pull down resistors

• Pull-up/pull-down resistors are a great way to prevent microcontroller GPIO inputs from assuming undefined values in embedded designs; however, they must be correctly sized (either weak or strong) based on power consumption requirements as well as existing circuitry (such as internal pull-up/pull-down resistors) to ensure proper circuit operation.

Using Pull-Up and Pull-Down Resistors@ Embedded Design

pull-up/down resistors can be used on both input and output pins, depending on application

• An embedded microcontroller utilizes input/output (IO) signals to communicate with the outside world. The simplest form of IO is commonly referred to as general purpose input/output (GPIO) where the GPIO voltage level can be high, low, or high-impedance. Pulling resistors are used to ensure GPIO is always in a valid state.

GPIO Input States on an Embedded Microcontroller

• GPIO on a microcontroller is usually configured as either input or output. As an input, the pin can take one of three states: low, high, and floating (also called high-impedance or tri-stated). When an input is driven above the input high threshold, it is high (or logic one). When driven below the input low threshold, the input is low (or logic zero). When in a high-impedance state, the input level is not reliably high nor low. To ensure an input value is always in a known state, a pull-up or pull-down resistor is used. A pull-up resistor pulls the signal to a high state unless it is driven low while a pull-down resistor puts the signal in a low state unless driven high.

Pull-up or Pull-down• The figure above illustrates a typical pull-up

resistor application. The resistor is connected between the power supply and a GPIO pin. A switch is then connected between the GPIO pin and ground. When the switch is open, there is (practically) zero current that flows from VCC through the resistor and into the GPIO pin. The voltage at the GPIO pin is given by the following equation derived from Ohm’s law: VGPIO = VCC - IR1*R1

In some systems, IPULLUP is a significant amount of current through the pull-up (or pull-down) resistor. Increasing the value of the resistor can reduce this current while simultaneously causing the pull-up or pull-down to be “weaker”.

Weak or Strong Pull-up/Pull-down Resistor

• A weak pull-up/pull-down resistor typically has a value of tens or hundreds of kilo-ohms. Strong pulling resistors have values of a few kilo-ohms and can override weak pulling resistors if both are used on the same microcontroller GPIO pin. The circuit below shows a GPIO pin with a weak internal pull-up resistor–most modern microcontroller designs have built-in pull-up and/or pull-down resistors on each GPIO pin–and a strong external pull-down resistor.

Weak or Strong Pull-up/Pull-down Resistor

• In order for the strong pull-down resistor to work properly, it must be correctly sized.During normal operation, the voltage at the GPIO pin must be below the input low voltage VIL as specified in the electrical characteristics section of the device’s datasheet. The voltage at the GPIO pin is calculated using a voltage divider:

VGPIO = VCC * R1 / (R2 + R1)

Note :

• The value of the strong pull-down must be low enough to make VGPIO < VIL.This ensures the voltage at the microcontroller GPIO pin is low (logic zero) when the switch is open. When the switch is closed, the signal is driven high–not because of the internal pull-up resistor but because it is directly connected to VCC.

IPULLUP

• Since there is no current through the resistor IR1=0, there is no voltage drop across R1 making the voltage at the GPIO input equal to VCC which causes the input to read “high”. When the switch is closed, the GPIO pin is connected directly to ground driving it “low”. As a side effect of closing the switch, current flows through the resistor according to the following equation (also from Ohm’s law):

IPULLUP = VCC/RPULLUP

Some examples of embedded systems -

• Mobile Phone, • Automotive Electronics, • Radio Frequency Identification (RFID) • Wireless Sensor Networks (WISENET), • Robotics,• Biomedical Applications, • Brain Machine Interface etc