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S3C2440A RISC MICROPROCESSOR UART
11-3
UART OPERATION
The following sections describe the UART operations that include data transmission, data reception, interrupt
generation, baud-rate generation, Loopback mode, Infrared mode, and auto flow control.
Data Transmission
The data frame for transmission is programmable. It consists of a start bit, 5 to 8 data bits, an optional parity bit
and 1 to 2 stop bits, which can be specified by the line control register (ULCONn). The transmitter can also
produce the break condition, which forces the serial output to logic 0 state for one frame transmission time. This
block transmits break signals after the present transmission word is transmitted completely. After the break signal
transmission, it continuously transmits data into the Tx FIFO (Tx holding register in the case of Non-FIFO mode).
Data Reception
Like the transmission, the data frame for reception is also programmable. It consists of a start bit, 5 to 8 data bits,
an optional parity bit and 1 to 2 stop bits in the line control register (ULCONn). The receiver can detect overrun
error, parity error, frame error and break condition, each of which can set an error flag.
— The overrun error indicates that new data has overwritten the old data before the old data has been read.
— The parity error indicates that the receiver has detected an unexpected parity condition.
— The frame error indicates that the received data does not have a valid stop bit.
— The break condition indicates that the RxDn input is held in the logic 0 state for a duration longer than one
frame transmission time.
Receive time-out condition occurs when it does not receive any data during the 3 word time (this interval follows
the setting of Word Length bit) and the Rx FIFO is not empty in the FIFO mode.