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BASIC UART
April 7, 2023 BASIC UART 1
PREPAID BY:RAHUL TIWARIROLL NO: 36
CONTENT
History Introduction Block diagram Working Structure Timing diagram Advantage and Disadvantage Application
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HISTORY
Need: A mean to connect peripherals RS-232 Serial Port UART First Applications: Teletypes or Visual
Display Units (VDU), Printers and Modems 8250: The first “PC” UART made by National UART Evolution:
8250 16450 16550 16C650A 16C850 Driven by Modem speeds, later by other applications Currently: sophisticated devices with numerous features
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INTRODUCTION
It is a type of "asynchronous receiver/transmitter“, communication standards such as EIA RS-232, RS-422 or RS-485. data format and transmission speeds A UART is usually an individual (or part of an) integrated circuit used for
serial communications over a computer or peripheral device serial port. types of UART
A dual UART, or DUART, combines two UARTs into a single chip.
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BLOCK DIAGRAM
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WORKING /OPERATION
takes bytes of data and transmits the individual bits in a sequential fashion. At the destination, re-assembles the bits into complete bytes
Transmission line are held high while no transmission/reception is taking place.
In the transmission of a sequence ,the active low start bit to the receiving UART that a new sequence of data is on its way. Lastly, a high stop bit is used to indicate the end of a block
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Frame Structure
UART is capable of transmitting/receiving 7 or 8 bits of data plus 2 or 3 framing bits.
One start bit, eight data bits and one stop bit, is the common configuration.
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Fig: General Form.
Fig: example of showing transmission of character ‘A’.
TRANSMITTER
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Transmitter output
RECEIVER
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ASMD CHART OF RECEIVER
RECEIVER OUTPUT
UART REGISTERS
I. Control Register - Contains settings for the UART. LCR: line control register(read/write) FCR:FIFO control register(write-only) IER: Interrupt enable register(read/write) MCR: Modem control register
II. Status Register - From its name, this contains information about the UART's condition or state.
IIR: Interrupt identification register(read-only) LSR: Line status register MSR: Modem status register(read-only)
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III. Receive Register - This is the where received data is temporarily stored. RBR: Receiver buffer register RHR : Receive Holding Register (read-only)
IV. Transmit Register - A buffer register/s for temporarily storing data to be sent.
THR: Transmitter holding register(write-only)
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Baud Rate Generator
UART clock =16 times original clock. The UART contains a programmable Baud Generator . Two 8-bit latches store the divisor in a 16-bit binary format.
DLL, divisor latch LSBDLM, divisor latch MSB(read/write)
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Fig: block diagram of baud rate generator
The baud rate generator is a frequency divider that generates baud rates according to the following equation:
Here: 1. BAUD = Baud rate2. f CK = Crystal Clock frequency3. UBR = Contents of the UBRRHI and UBRR registers, (0-4095)
BAUD GENERATOR OUTPUT
ADVANTAGE
The UART system can tolerate a moderate amount of system noise without losing any information.
Supports all data rates from 9600 to 921600 band Internal diagnostic capabilities:
- Loop-back controls for communications link fault isolation- Break, parity, overrun, framing error simulation
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DISADVANTAGE
As we increase the baud rate, distance of communication will decrease.
Due to asynchronous transmission, it is not accurate compared to synchronous transmission.
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APPLICATION
Inter board communications Simple PC to Board interface For all serial communications Industrial
Heating-Ventilation-Air-Conditioning (HVAC),Security, Telemetry, Sensors, Medical, Test & Measurement, Data Terminals, Video Conf. Systems, Copiers, Printers, Data Recorder, Avionic, Robotic.
Telecom:Network Server Management (24/7, QoS, Redundancy), Hub, Router, Switch, Console Management, Keyboard-Video-Mouse (KVM) Switches, Home Networks, Bluetooth Devices, PDA Modules. Point of-Sale (POS)
Credit Authorization Systems, Handheld and Inventory Terminals, Banking ATM, Ticketing and Vending, Tolls Collection Systems, Car Parking Systems.
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Inter board communication:
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Telecom Application:
Server Management: Easy connections Simple protocol Chain to other systems or peripherals via RS-232/485
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REFRENCE
http://www.ftdichip.com/Support/Documents/TechnicalNotes/TN_111%20What%20is%20UART.pdf
http://layadcircuits.com/layad_articles/UART_Basics.htm http://www.cse.sc.edu/~jimdavis/Courses/CSCE-612(Spring03)/
CSCE612-Project-2-uart8251-030214.pdf http://www.seminarprojects.com/Thread-basic-uart-full-report http://www.rosehulman.edu/~simoni/Classes/EC551/ProjectInfo/
UARTChallenge.pdf http://www.xmos.com/system/files/uart-tutorial.pdf http://www.mikroe.com/eng/chapters/view/43/chapter-10-uart-module/ http://www.exar.com/uploadedFiles/ICI/UARTIntro_100_030507.pdf http://en.wikipedia.org/wiki/Universal_asynchronous_receiver/transmitter www.cosmiac.org/pdfs/T4_UART_TUTORIAL_vf.doc
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Thank You
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