uart

Universal Asynchronous
Receiver/Transmitter
UARTECEn/CS 22420 UART
Page 1© 2003-2006
BYUWhy use a UART• A UART may be used when:
– High speed is not required
– A cheap communication line between two devices
is required
• Asynchronous serial communication is very cheap
– Requires a transmitter and/or receiver
– Single wire for each direction (plus ground wire)
– Relatively simple hardware
– Asynchronous because the
• PC devices such as mice and modems used to often
be asynchronous serial devices
ECEn/CS 22420 UART
Page 2© 2003-2006
BYUUART Uses
• PC serial port is a UART!
• Serializes data to be sent over serial cable
– De-serializes received data
Serial
PortSerial
CableSerial
PortSerial
CableDeviceECEn/CS 22420 UART
Page 3© 2003-2006
BYUUART Uses
• Communication between distant computers
– Serializes data to be sent to modem
– De-serializes data received from modem
Serial
CablePhone
Line
Phone
LineSerial
CableModemModemECEn/CS 22420 UART
Page 4© 2003-2006
BYUUART Uses
• Used to be commonly used for internet accessPhone
LineInternet
InternetPhone
LineSerial
CableModemECEn/CS 22420 UART
Page 5© 2003-2006
BYUUART Uses
• Used to be used for mainframe access
– A mainframe could have dozens of serial ports
MainframeSerial
CablesTerminalTerminal
TerminalTerminalECEn/CS 22420 UART
Page 6© 2003-2006
BYUUART Uses
• Becoming much less common
• Largely been replaced by faster, more
sophisticated interfaces
– PCs: USB (peripherals), Ethernet (networking)
– Chip to chip: I2C, SPI• Still used today when simple low speed
communication is neededECEn/CS 22420 UART
Page 7© 2003-2006
BYUUART Functions
• Outbound data
– Convert from parallel to serial
– Add start and stop delineators (bits)
– Add parity bit• Inbound data
–…

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