Uart Afc Interface - Samsung S3C2416 User Manual

UART
2.1.3 Auto Flow Control (AFC)
UART 0, UART 1 and UART 2 support auto flow control with nRTS and nCTS signals. In AFC, nCTS signals
control the operation of the transmitter, and nRTS depends on the condition of the receiver.
The UART's transmitter transfers the data in FIFO only when nCTS signals are activated(Low) (In AFC, nCTS
means that other UART's FIFO is ready to receive data or not).
Before the UART receives data, nRTS signal has to be activated(Low) when its receive FIFO has a spare space
more than 32-byte(FIFO contains less than 32-byte). And nRTS signal has to be inactivated(High) when its
receive FIFO has a spare under 32-byte(FIFO contains equal or more than 32-byte) in case of RTS trigger level is
32byte. (In AFC, nRTS means that its own receive FIFO is ready to receive data or not).
Transmission Case in UART A
UART A
UART 3 does not support AFC function, because the S3C2416 has no nRTS 3 and nCTS 3.
S3C2416's AFC does not support the RS-232C interface.
FIFO FIFO Spare
Contains Space
33 byte 31 byte
32 byte
32 byte
31 byte
33 byte
30 byte
34 byte
14-4
UART B
TxD RxD
nCTS nRTS
Figure 14-2. UART AFC Interface
Table 14-1. Example of nRTS signal change by FIFO Spare size
(In case of Reception Case in UART A)
RX side
nRTS
Signal
High Not ready to receive
High Not ready to receive
Low Ready to Receive
Low Ready to Receive
Reception Case in UART A
UART A
nRTS
NOTE
nRTS
Meaning
High
High
Low
Low
S3C2416X RISC MICROPROCESSOR
UART B
RxD TxD
nCTS
TX side
nCTS
Signal Meaning
Don't send data to RX side
Don't send data to RX side
Send data to RX side
Send data to RX side
nCTS