Samsung S5PC100 User Manual page 627

S5PC100 USER'S MANUAL (REV1.0)
3 DESCRIPTION
The following sections describe UART operations, including data transmission, data reception, interrupt
generation, baud-rate generation, Loop-back mode, infrared mode, and auto flow control.
3.1 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 are 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 case of Non-FIFO mode).
3.2 DATA RECEPTION
Similar to data 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 detects
overrun error, parity error, frame error and break condition, each of which sets an error flag.
•
Overrun error indicates that new data has overwritten the old data before the old data has been read.
•
Parity error indicates that the receiver has detected an unexpected parity condition.
•
Frame error indicates that the received data does not have a valid stop bit.
•
Break condition indicates that the RxDn input is held in the logic 0 state for more than one frame transmission
time.
Receive time-out condition occurs if no data is received 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.
3.3 AUTO FLOW CONTROL(AFC)
The S5PC100's UART0 and UART1 support auto flow control with nRTS and nCTS signals. UART2 supports auto
flow control if TxD3 and RxD3 are set as nRTS2 and nCTS2 by GPA1CON(GPIO SFR). In case, it can be
connected to external UARTs. To connect a UART to a Modem, disable auto flow control bit in UMCONn register
and control the signal of nRTS by software.
In AFC, nRTS depends on the condition of the receiver and nCTS signals control the operation of the transmitter.
The UART's transmitter transfers the data in FIFO if nCTS signals are activated (In AFC, nCTS means that other
UART's FIFO is ready to receive data). Before UART receives the data, nRTS must be activated if its receive
FIFO has more than 2-byte as spare. The nRTS must be inactivated if its receive FIFO has less than 1-byte as
spare (In AFC, nRTS means that its own receive FIFO is ready to receive data).
UART
8.1-3