REV. 1.0.2 66MHZ PCI BUS OCTAL UART WITH POWER MANAGEMENT SUPPORT 4.7 Receiver The receiver section contains an 8-bit" />
參數(shù)資料
型號(hào): XR17V258IV
廠商: Exar Corporation
文件頁數(shù): 38/69頁
文件大?。?/td> 0K
描述: IC UART PCI BUS OCTAL 144LQFP
產(chǎn)品變化通告: Leaded UART, V&I Obsolescence 11/Apr/2011
標(biāo)準(zhǔn)包裝: 60
特點(diǎn): *
通道數(shù): 8
FIFO's: 64 字節(jié)
規(guī)程: RS485
電源電壓: 3.3V,5V
帶自動(dòng)流量控制功能:
帶IrDA 編碼器/解碼器:
帶故障啟動(dòng)位檢測(cè)功能:
帶調(diào)制解調(diào)器控制功能:
安裝類型: 表面貼裝
封裝/外殼: 144-LQFP
供應(yīng)商設(shè)備封裝: 144-LQFP(20x20)
包裝: 托盤
XR17V258
43
REV. 1.0.2
66MHZ PCI BUS OCTAL UART WITH POWER MANAGEMENT SUPPORT
4.7
Receiver
The receiver section contains an 8-bit Receive Shift Register (RSR) and Receive Holding Register (RHR). The
RSR uses the 16X or 8X clock for timing. It verifies and validates every bit on the incoming character in the
middle of each data bit. On the falling edge of a start or false start bit, an internal receiver counter starts
counting at the 16X or 8X clock rate. After 8 or 4 clocks the start bit period should be at the center of the start
bit. At this time the start bit is sampled and if it is still a logic 0 it is validated. Evaluating the start bit in this
manner prevents the receiver from assembling a false character. The rest of the data bits and stop bits are
sampled and validated in this same manner to prevent false framing. If there were any error(s), they are
reported in the LSR register bits [4:1]. Upon unloading the receive data byte from RHR, the receive FIFO
pointer is bumped and the error flags are immediately updated to reflect the status of the data byte in RHR
register. RHR can generate a receive data ready interrupt upon receiving a character or delay until it reaches
the FIFO trigger level. Furthermore, data delivery to the host is guaranteed by a receive data ready time-out
function when receive data does not reach the receive FIFO trigger level. This time-out delay is 4 word lengths
as defined by LCR bits [1:0] plus 12 bits time. The RHR interrupt is enabled by IER bit [0].
4.7.1
Receiver Operation in non-FIFO Mode
FIGURE 17. RECEIVER OPERATION IN NON-FIFO MODE
Receive Data Shift
Register (RSR)
Receive
Data Byte
and Errors
RHR Interrupt (ISR bit-2)
Receive Data
Holding Register
(RHR)
RXFIFO1
16X or 8X Clock
(8XMODE Register)
Receive Data Characters
Data Bit
Validation
Error
Flags in
LSR bits
4:2
4.7.2
Receiver Operation with FIFO
FIGURE 18. RECEIVER OPERATION IN FIFO AND FLOW CONTROL MODE
Receive Data Shift
Register (RSR)
RXFIFO1
16X or 8X Sampling
Clock (8XMODE Reg.)
E
rro
rFl
ags
(64
-set
s)
E
rro
rFl
ags
in
LS
R
bi
ts
4:
2
64 bytes by 11-
bit wide FIFO
Receive Data Characters
FIFO Trigger=48
Example:
- FIFO trigger level set at 48 bytes
- RTS/DTR hyasteresis set at +/-8 chars.
Data fills to 56
Data falls to 40
Data Bit
Validation
Receive Data
FIFO
(64-byte)
Receive
Data
Receive Data
Byte and Errors
RHR Interrupt (ISR bit-2) is programmed
at FIFO trigger level (RXTRG).
FIFO is Enable by FCR bit-0=1
RTS#/DTR# de-asserts when data fills above
the trigger level to suspend remote transmitter.
Enable by EFR bit-6=1, MCR bit-2.
RTS#/DTR# re-asserts when data falls below
the trigger level to restart remote transmitter.
Enable by EFR bit-6=1, MCR bit-2.
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