REV. 1.2.2 UNIVERSAL (3.3V AND 5V) PCI BUS OCTAL UART 33 5.3 Receiver The receiver section contains an 8-bit Receive " />
參數(shù)資料
型號: XR17D158IV-F
廠商: Exar Corporation
文件頁數(shù): 27/73頁
文件大?。?/td> 0K
描述: IC UART PCI BUS OCTAL 144LQFP
產品培訓模塊: UART Product Overview
標準包裝: 60
特點: *
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:
帶調制解調器控制功能:
安裝類型: 表面貼裝
封裝/外殼: 144-LQFP
供應商設備封裝: 144-LQFP(20x20)
包裝: 托盤
其它名稱: 1016-1292
xr
XR17D158
REV. 1.2.2
UNIVERSAL (3.3V AND 5V) PCI BUS OCTAL UART
33
5.3
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 1- 4. 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[1:0] plus 12 bits time. The RHR interrupt is enabled by IER bit-0.
5.3.1
Receive Holding Register (RHR)
The receive holding register is an 8-bit register that holds a receive data byte from the receive shift register
(RSR). It provides the receive data interface to the host processor. The host reads the receive data byte on this
register whenever a data byte is transferred from the RSR. RHR also part of the receive FIFO of 64 bytes by
11-bit wide, 3 extra bits are for the error flags to be in LSR register. When the FIFO is enabled by FCR bit-0, it
acts as the first-out register of the FIFO as new data are put over the first-in register. The receive FIFO pointer
is bumped after the RHR register is read. Also, the error flags associated with the data byte are immediately
updated onto the line status register (LSR) bits 1-4.
5.3.2
Receiver Operation in non-FIFO Mode
FIGURE 14. 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
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