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UNIVERSAL ASYNCRONOUS TRANSMITTER AND RECEIVER.pptx
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- 2. What is UART â˘Universal asynchronous receiver/transmitter ⢠Protocol for exchanging serial data between two devices ⢠Uses only two wires - TX to RX (each direction) ⢠Data is transmitted in the form of frames
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- 4. UART COMMUNICATION ⢠InUART communication, two UARTs communicate directly with each other. ⢠The transmitting UART converts parallel data from a controlling device like a CPU into serial form, transmits it in serial to the receiving UART, which then converts the serial data back into parallel data for the receiving device. ⢠Only two wires are needed to transmit data between two UARTs. Data flows from the Tx pin of the transmitting UART to the Rx pin of the receiving UART
- 5. ⢠UARTs transmitdata asynchronously, which means there is no clock signal to synchronize the output of bits from the transmitting UART to the sampling of bits by the receiving UART. ⢠Instead of a clock signal, the transmitting UART adds start and stop bits to the data packet being transferred. ⢠These bits define the beginning and end of the data packet so the receiving UART knows when to start reading the bits.
- 6. ⢠When thereceiving UART detects a start bit, it starts to read the incoming bits at a specific frequency known as the baud rate. ⢠Baud rate is a measure of the speed of data transfer, expressed in bits per second (bps). ⢠Both UARTs must operate at about the same baud rate.
- 7. STEPS OF UARTTRANSMISSION ⢠The transmitting UART receives data in parallel from the data bus ⢠The transmitting UART adds the start bit, parity bit, and the stop bit(s) to the data frame ⢠The entire packet is sent serially from the transmitting UART to the receiving UART. The receiving UART samples the data line at the pre-configured baud rate ⢠The receiving UART discards the start bit, parity bit, and stop bit from the data frame ⢠The receiving UART converts the serial data back into parallel and transfers it to the data
- 8. UART MODULES The UARTserial communication module divided in to three sub modules 1. UART transmitter 2. UART receiver 3. Baud rate generator
- 9. UART Character Transmission â˘Below is a timing diagram for the transmission of a single byte ⢠Uses a single wire for transmission ⢠Each block represents a bit that can be a mark (logic â1â, high) or space (logic â0â, low)
- 10. UART Character Transmission â˘Each bit has a fixed time duration determined by the transmission rate ⢠Example: a 1200 bps (bits per second) UART will have a 1/1200 s or about 833.3 Âľs bit width
- 11. UART Character Transmission â˘In the configuration shown, it takes 10 bits to send 7 bits of data ⢠The start bit marks the beginning of a new word ⢠When detected, the receiver synchronizes with the new data stream
- 12. UART Character Transmission â˘Next follows the data bits (7 or 8) ⢠The least significant bit is sent first ⢠The parity bit is added to make the number of 1âs even (even parity) or odd (odd parity). ⢠This bit can be used by the receiver to check for transmission errors
- 13. UART Character Transmission â˘The stop bit marks the end of transmission ⢠Receiver checks to make sure it is â1â ⢠Separates one word from the start bit of the next word
- 14. UART Transmission Example â˘Send the ASCII letter âWâ (1010111)
- 15. UART RECEPTION ⢠Duringthe UART reception the serial data and receiving clock are asynchronous. So it is very important to correctly determine the start bit of a frame data. ⢠When the receiving UART detects the high to low voltage transition, it begins reading the bits in the data frame at the frequency of the baud rate. ⢠Receiver look for a stop bit after complete data transmission. If stop bit does not appear when it is supposed to be UART will report framing error to the host.
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