UART Trivia Questions & FAQ

Universal Asynchronous Receiver Transmitter

The XIN and XOUT pins are used to connect an external crystal. These pins can also connect external clock.

Intel 8250 is a UART which is commonly used.

The timing is defined by the baud rate in which both the transmitter and receiver are used. The baud rate is supplied by the counter or an external timer called baud rate generator which generate a clock signal.

UART is an on-chip peripheral of Microcontroller which can be used for Synchronous and Asynchronous serial communication in which data format and transmission speeds are configurable.

The standard Speed of UART is up to 1 Mbps.

The 8250 UART has one character buffer for the receiver and the transmitter each, which meant that communications software performed poorly at speed above 9600bits/sec, especially it operating under a multitasking system or if handling interrupts from disk controllers.

LSB to MSB

Hyper Terminal is a communications software (or) Hyper Terminal is a program that you can use to connect to other computers. With Hyper Terminal, the user can connect and transfer files between the two computers.

In Computing, a serial port is a serial communication interface through which information Transfers in (or) out sequentially one bit a time.

1)Size of data in the frame is Limited.
2)It is suitable for communication between two devices.

UART Errors
Framing error: A framing error occurs when the designated start and stop bits are not found. If the data line is not in the expected state when the stop bit is expected, a framing error will occur.
Underrun error: An Underrun error occurs when the UART transmitter has completed sending a character and the transmit buffer is empty. In asynchronous mode, this is treated as an indication that no data remains to be transmitted.
Overrun error:
Parity error: A parity error occurs when the parity of the number of 1 bit disagrees with that specified by the parity bit. Using parity is optional, so this error will only occur if parity checking has been enabled. Single bit error only can identify, can?t find two or more bits? error
Break condition: A break condition occurs when the receiver input is at the space level for longer than some duration of time, typically, for more than a character time. You need to set a break to detect interruptions in registers. Setting this bit enables the SCI to generate an error interrupt if a break condition is detected on the SCIRX pin.

Only two wires interface.
No clock signal is necessary.
Error checking Feature allows: Has a parity bit check
The structure of the data packet can be changed as long as both sides are set up for it
Widely Used method and well documented

1)GSM
2)GPS
3)RFID

Transmitter Interrupt
Receiver Interrupts
Wakeup Interrupts
Error Interrupts (Parity errors (PE), Frame errors (FE), Break Detect errors (BRKDT), Overrun errors (OE), Bit errors (BE))

Full Duplex

UART is two wired protocol.
1)TxD(Transmit Data)
2)RxD(Receive Data)

The data can be detected by the local clock reference which is generated from the baud rate generator.