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UART
AUTO FLOW CONTROL(AFC)
The S3C6400 UART 0 and UART 1 support auto flow control with nRTS and nCTS signals. In case, it can be
connected to external UARTs. If you want to connect a UART to a Modem, you must 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 only when nCTS signals are activated (in AFC, nCTS means
that other UART's FIFO is ready to receive data). Before the UART receives data, nRTS has to be activated
when its receive FIFO has a spare
spare under 1-byte (in AFC, nRTS means that its own receive FIFO is ready to receive data).
Transmission case in
UART A
TxD
nCTS
EXAMPLE OF NON AUTO-FLOW CONTROL (CONTROLLING NRTS AND NCTS BY SOFTWARE)
- Rx operation with FIFO
1.
Select receive mode (Interrupt or DMA mode).
2.
Check the value of Rx FIFO count in UFSTATn register. If the value is less than 15, you must set the
value of UMCONn[0] to '1' (activating nRTS), and if it is equal or larger than 15 you must set the value
to '0' (inactivating nRTS).
3.
Repeat the Step 2.
- Tx operation with FIFO
1.
Select transmit mode (Interrupt or DMA mode).
2.
Check the value of UMSTATn[0]. If the value is '1' (activating nCTS), you must write the data to Tx
FIFO register.
3.
Repeat the Step 2.
31-4
Preliminary product information describe products that are in development,
for which full characterization data and associated errata are not yet available.
Specifications and information herein are subject to change without notice.
of
more than 2-byte and has to be inactivated when its receive FIFO has a
UART A
UART B
RxD
nRTS
Figure 31-2 UART AFC interface
S3C6400 RISC MICROPROCESSOR
Reception case in
UART A
UART A
UART B
RxD
TxD
nRTS
nCTS
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