UART ppt

Universal Asynchronous Receiver/Transmitter(UART)

Project Guide: Er. Jay Kumar

Submitted by: Mayank Sharma-0800431042 Uday Bhan Singh-0800431074Shantanu Tripathi-0800431063Chandra Prakash-0800431016

PROJECT PRESENTATION ON

EEC-754

CONTENTS

• INTRODUCTION

• UART BLOCK DIAGRAM

• TRANSMITTER MODULE

• RECEIVER MODULE

• INPUT / OUTPUT PORTS

• APPLICATIONS OF UART

• DESIGNING TOOL: VHDL

• REFERENCES

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INTRODUCTION

• The UART (universal asynchronous receiver and transmitter) module provides asynchronous serial communication with external devices such as modems and other computers.

• The UART can be used to control the process of breaking parallel data from the PC down into serial data that can be transmitted and vice versa for receiving data.

• The UART allows the devices to communicate without the need to be synchronized.

• The UART consists of one receiver module and one transmitter module.

• Those two modules have separate inputs and outputs for most of their control lines, the lines that are shared by both modules are the bi-directional data bus, master clock (mclkx16) and reset.

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• A UART may be used when:

– High speed is not required

– An inexpensive communication link between two devices is required

• UART communication is very cheap

– Single wire for each direction (plus ground wire.

– Asynchronous because no clock signal is transmitted

– Relatively simple hardware

• PC devices such as mouse and modems used to often use UARTs for communication to the PC

Need of UART

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BLOCK DIAGRAM

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UART Functions

• Transmitter

– Convert from parallel to serial

– Add start and stop delineators (bits)

– Add parity bit

• Receiver

– Convert from serial to parallel

– Remove start and stop delineators (bits)

– Check and remove parity bit

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TRANSMITTER MODULE

As soon as data is deposited in the shift

register after completion of the previous

character, the UART hardware generates a

start bit, shifts the required number of data

bits out to the line, generates and appends

the parity bit (if used), and appends the stop

bits

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Specifications

• Parameters: 8 data bits, 1 stop bit, even or odd parity

• Inputs:

– Din[7:0]: 8-bit parallel data input

– Send: Instructs transmitter to initiate a transmission

– Parity Select: Selects even parity (Parity Select=0) or odd parity (Parity

Select=1)

• Outputs:

– Dout: Serial data output

– Busy: Tells the host it’s busy sending a character

UART Transmitter

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RECEIVER MODULE

The receiver tests the state of the incoming signal on each clock pulse, looking for the beginning of the start bit

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Specifications

• Parameters: 8 data bits, 1 start bit, even or odd parity

• Inputs:

– Din: Serial data output

– overrun: Tells the host it’s busy receiving a character

• Outputs:

– Dout[7:0]: 8-bit parallel data input

– read: Instructs receiver to initiate a reception of data.

– Parity Select: Selects even parity (Parity Select=0) or odd parity (Parity

Select=1)

UART Receiver

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Input/output module

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Symbol Type Description

mclkx16 Input Master input clock for internal baud rate generation

reset Input Master reset

parityerr output Indicates whether a parity error was detected during the receiving of a data frame

framingerr output Indicates if the serial data format sent to the rx input did not match the proper UART data format

overrun output Indicates whether new data sent in is overwriting the previous data received that has not been read out yet.

rxrdy output Indicates new data has been received and is ready to be read out.

txrdy output Indicates new data has been written to the transmitter

Symbol Type Description

read Input Active low strobe signal, used for reading data out from the receiver.

write Input Active low strobe signal, used for writing data in to transmitter.

data (7 down to 0)

In/Out Bi-directional data bus for sending/receiving data across the UART

tx Output Transmitter serial output. Held high when no transmission occurring and when resetting

rx Input Receiver serial input. Pulled-up when no transmissions taking place.

UART Uses

• PC serial port is a UART!– Serializes data to be sent over serial cable

– De-serializes received data

SerialCable

SerialCable

Device

SerialPort

SerialPort

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(contd..)

• Communication between distant computers– Serializes data to be sent to modem

– De-serializes data received from modem

SerialCable

SerialCable

PhoneLine

PhoneLine

Modem

Modem

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(contd..)

• Used to be commonly used for internet access

SerialCable

PhoneLine

PhoneLine

Modem

InternetInternet

Server

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UART Character Transmission

• In the configuration shown, it takes 11 bits to send 8 bits of data

• Transmission efficiency is 8/11, or 72.72%

Stop bitStart bit 8 data bits Parity bit

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UART Transmission Example

• Send the ASCII letter ‘W’ (10101110)

Line idling Start bitParity bit(odd parity) Stop bit

Line idling again

Mark

Space

8 data bits – Least significant bit first

1 1 1 0 1 0 10 0

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Mark

Space

UART Character Reception

Receiver should sample in middle of bits

Start bit says a character is coming,receiver resets its timers

Receiver uses a timer (counter) to time when it samples.Transmission rate (i.e., bit duration) must be known!

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UART Options

• UARTs usually have programmable options:– Data: 7 or 8 bits

– Parity: even, odd, none

– Stop bits: 1, 2

– Baud rate: 300, 1200, 2400, 4800, 9600, 19.2k, 38.4k, 57.6k, 115.2k…

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UART Options

• Baud Rate– The “symbol rate” of the transmission system

– For a UART, same as the number of bits per second (bps)

– Each bit is 1/(rate) seconds wide

• Example:– 9600 baud 9600 Hz

– 9600 bits per second (bps)

– Each bit is 1/(9600 Hz) ≈ 104.17 µs long

Not the data throughput rate!

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VHDL :- :- Very high speed integrated circuit hardware description language

• An initiative funded by the United States Department of Defense in the 1980s that led to the creation of VHDL. Its first version was VHDL 87, later upgraded to the so-called VHDL 93. VHDL was the original and first hardware description language to be standardized by the Institute of Electrical and Electronics Engineers, through the IEEE 1076 standard.

• VHDL is a hardware description language. It describes the behavior of an electronic circuit or system, from which the physical circuit or system can then be attained (implemented).

Tool Used

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Design Flow

VHDL :- Very high speed integrated circuit hardware VHDL :- Very high speed integrated circuit hardware

description language.description language.

Specification

programming

Simulation(Compile)

Synthesis

Implementation onFPGA/CPLD

Hardware

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Modeling of VHDL

1.1. Data Flow modeling (Boolean Expression or Small Circuit)Data Flow modeling (Boolean Expression or Small Circuit)

2.2. Behavioural Modeling ( Truth Table or input / output relation (for Behavioural Modeling ( Truth Table or input / output relation (for

sequential )sequential )

3.3. Structural Modeling (Large circuits, Interconnections of small Structural Modeling (Large circuits, Interconnections of small

modular (circuits)modular (circuits)

4.4. Mixed Modeling Mixed Modeling

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1.Doughlas L. Perry VHDL programming 4TH Edition.2. Karen Parnell & Nick Mehta Programmable Logic Design 2nd Edition.3. Norhuzaimin, J, Maimun, H.H, Dept. of Electron., Univ. Malaysia Sarawak, Applied Electromagnetics, 2005. APACE 2005. Asia-Pacific Conference on uart.4. Peter J. Ashenden VHDL Quick Start 2nd Edition.5. Shouqian Yu,   Lili Yi,   Weihai Chen,  Zhaojin Wen Beijing Univ. of Aeronaut. & Astronaut., Beijing, Industrial Electronics and Applications, 2007. ICIEA 2007. 2nd IEEE Conference on uart.6. Teemu Pitkanen VHDL Basics.7. Zhichao Zhang,  Wuchen Wu   VLSI & Syst. Lab., Beijing Univ. of Technol., Beijing, China  Computer Engineering and Technology (ICCET), 2010 2nd International Conference on uart.8. www.ieeeexplore.com9.www.howstuffworks.com

REFERENCES

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Thanks