REV. 2.1.3 16 2.14 Auto CTS Flow Control Automatic CTS flow control is u" />
參數(shù)資料
型號: XR16C2850IM-F
廠商: Exar Corporation
文件頁數(shù): 8/51頁
文件大小: 0K
描述: IC UART FIFO 128B DUAL 48TQFP
標準包裝: 250
特點: *
通道數(shù): 2,DUART
FIFO's: 128 字節(jié)
規(guī)程: RS232,RS485
電源電壓: 2.97 V ~ 5.5 V
帶自動流量控制功能:
帶IrDA 編碼器/解碼器:
帶故障啟動位檢測功能:
帶調(diào)制解調(diào)器控制功能:
帶CMOS:
安裝類型: 表面貼裝
封裝/外殼: 48-TQFP
供應(yīng)商設(shè)備封裝: 48-TQFP(7x7)
包裝: 托盤
其它名稱: 1016-1275
XR16C2850
xr
2.97V TO 5.5V DUAL UART WITH 128-BYTE FIFOS
REV. 2.1.3
16
2.14
Auto CTS Flow Control
Automatic CTS flow control is used to prevent data overrun to the remote receiver FIFO. The CTS# input is
monitored to suspend/restart the local transmitter. The auto CTS flow control feature is selected to fit specific
application requirement (see Figure 11):
Enable auto CTS flow control using EFR bit-7.
With the Auto CTS function enabled, the UART will suspend transmission as soon as the stop bit of the
character in the Transmit Shift Register has been shifted out. Transmission is resumed after the CTS# input is
re-asserted (LOW), indicating more data may be sent.
Enable CTS interrupt through IER bit-7 (after setting EFR bit-4). The UART issues an interrupt when the
CTS# pin is de-asserted (HIGH) during Auto CTS flow control mode: ISR bit-5 will be set to 1.
FIGURE 11. AUTO RTS AND CTS FLOW CONTROL OPERATION
The local UART (UARTA) starts data transfer by asserting RTSA# (1). RTSA# is normally connected to CTSB# (2) of
remote UART (UARTB). CTSB# allows its transmitter to send data (3). TXB data arrives and fills UARTA receive FIFO
(4). When RXA data fills up to its receive FIFO trigger level, UARTA activates its RXA data ready interrupt (5) and con-
tinues to receive and put data into its FIFO. If interrupt service latency is long and data is not being unloaded, UARTA
monitors its receive data fill level to match the upper threshold of RTS delay and de-assert RTSA# (6). CTSB# follows
(7) and request UARTB transmitter to suspend data transfer. UARTB stops or finishes sending the data bits in its trans-
mit shift register (8). When receive FIFO data in UARTA is unloaded to match the lower threshold of RTS delay (9),
UARTA re-asserts RTSA# (10), CTSB# recognizes the change (11) and restarts its transmitter and data flow again until
next receive FIFO trigger (12). This same event applies to the reverse direction when UARTA sends data to UARTB
with RTSB# and CTSA# controlling the data flow.
RTSA#
CTSB#
RXA
TXB
Transmitter
Receiver FIFO
Trigger Reached
Auto RTS
Trigger Level
Auto CTS
Monitor
RTSA#
TXB
RXA FIFO
CTSB#
Remote UART
UARTB
Local UART
UARTA
ON
OFF
ON
Suspend
Restart
RTS High
Threshold
Data Starts
ON
OFF
ON
Assert RTS# to Begin
Transmission
1
2
3
4
5
6
7
Receive
Data
RTS Low
Threshold
9
10
11
Receiver FIFO
Trigger Reached
Auto RTS
Trigger Level
Transmitter
Auto CTS
Monitor
RTSB#
CTSA#
RXB
TXA
INTA
(RXA FIFO
Interrupt)
RX FIFO
Trigger Level
RX FIFO
Trigger Level
8
12
RTSCTS1
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