REV. 1.2.1 8 2.6 Channel A and B Internal Registers Each UART channel in the 2750 has a set " />
參數(shù)資料
型號: XR16L2750IM-F
廠商: Exar Corporation
文件頁數(shù): 47/48頁
文件大?。?/td> 0K
描述: IC UART FIFO 64B DUAL 48TQFP
標(biāo)準(zhǔn)包裝: 250
特點: *
通道數(shù): 2,DUART
FIFO's: 64 字節(jié)
規(guī)程: RS232,RS485
電源電壓: 2.25 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: 1016-1280
XR16L2750
xr
2.25V TO 5.5V DUART WITH 64-BYTE FIFO
REV. 1.2.1
8
2.6
Channel A and B Internal Registers
Each UART channel in the 2750 has a set of enhanced registers for control, monitoring and data loading and
unloading. The configuration register set is compatible to those already available in the standard single
16C550 and dual ST16C2550. These registers function as data holding registers (THR/RHR), interrupt status
and control registers (ISR/IER), a FIFO control register (FCR), receive line status and control registers (LSR/
LCR), modem status and control registers (MSR/MCR), programmable data rate (clock) divisor registers (DLL/
DLM), and a user accessible Scratchpad Register (SPR).
Beyond the general 16C2550 features and capabilities, the 2750 offers enhanced feature registers (EMSR,
FLVL, EFR, Xon/Xoff 1, Xon/Xoff 2, FCTR, TRG, FC) that provide automatic RTS and CTS hardware flow
control, Xon/Xoff software flow control, automatic RS-485 half-duplex direction output enable/disable, FIFO
trigger level control, and FIFO level counters. All the register functions are discussed in full detail later in
2.7
DMA Mode
The device does not support direct memory access. The DMA Mode (a legacy term) in this document doesn’t
mean “direct memory access” but refers to data block transfer operation. The DMA mode affects the state of
the RXRDY# A/B and TXRDY# A/B output pins. The transmit and receive FIFO trigger levels provide additional
flexibility to the user for block mode operation. The LSR bits 5-6 provide an indication when the transmitter is
empty or has an empty location(s) for more data. The user can optionally operate the transmit and receive
FIFO in the DMA mode (FCR bit-3=1). When the transmit and receive FIFO are enabled and the DMA mode is
disabled (FCR bit-3 = 0), the 2750 is placed in single-character mode for data transmit or receive operation.
When DMA mode is enabled (FCR bit-3 = 1), the user takes advantage of block mode operation by loading or
unloading the FIFO in a block sequence determined by the programmed trigger level. In this mode, the 2750
sets the TXRDY# pin when the transmit FIFO becomes full, and sets the RXRDY# pin when the receive FIFO
becomes empty. The following table shows their behavior. Also see Figures 18 through 23.
TABLE 1: CHANNEL A AND B SELECT
CSA#
CSB#
FUNCTION
1
UART de-selected
0
1
Channel A selected
1
0
Channel B selected
0
Channel A and B selected
TABLE 2: TXRDY# AND RXRDY# OUTPUTS IN FIFO AND DMA MODE
PINS
FCR BIT-0=0
(FIFO DISABLED)
FCR BIT-0=1 (FIFO ENABLED)
FCR Bit-3 = 0
(DMA Mode Disabled)
FCR Bit-3 = 1
(DMA Mode Enabled)
RXRDY# A/B LOW = 1 byte.
HIGH = no data.
LOW = at least 1 byte in FIFO.
HIGH = FIFO empty.
HIGH to LOW transition when FIFO reaches the
trigger level, or time-out occurs.
LOW to HIGH transition when FIFO empties.
TXRDY# A/B LOW = THR empty.
HIGH = byte in THR.
LOW = FIFO empty.
HIGH = at least 1 byte in FIFO.
LOW = FIFO has at least 1 empty location.
HIGH = FIFO is full.
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