REV. 1.0.2 2.6 DMA Mode The device does n" />
參數(shù)資料
型號: XR16M2551IL32TR-F
廠商: Exar Corporation
文件頁數(shù): 2/51頁
文件大?。?/td> 0K
描述: IC UART FIFO 16B DUAL 32QFN
標(biāo)準(zhǔn)包裝: 3,000
特點: *
通道數(shù): 2,DUART
FIFO's: 16 字節(jié)
規(guī)程: RS232,RS422
電源電壓: 1.62 V ~ 3.63 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:
安裝類型: 表面貼裝
封裝/外殼: 32-VFQFN 裸露焊盤
供應(yīng)商設(shè)備封裝: 32-QFN 裸露焊盤(5x5)
包裝: 帶卷 (TR)
XR16M2551
10
HIGH PERFORMANCE LOW VOLTAGE DUART WITH 16-BYTE FIFO AND POWERSAVE FEATURE
REV. 1.0.2
2.6
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 M2551 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 selected trigger level. In this mode, the M2551 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 19 through 24.
2.7
INTA and INTB Outputs
The INTA and INTB interrupt output changes according to the operating mode and enhanced features setup.
Table 4 and 5 summarize the operating behavior for the transmitter and receiver. Also see Figures 19
through 24.
TABLE 3: 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
TABLE 4: INTA AND INTB PINS OPERATION FOR TRANSMITTER
FCR BIT-0 = 0
(FIFO DISABLED)
FCR BIT-0 = 1 (FIFO ENABLED)
INTA/B Pin
LOW = A byte in THR
HIGH = THR empty
LOW = FIFO above trigger level
HIGH = FIFO below trigger level or FIFO empty
TABLE 5: INTA AND INTB PIN OPERATION FOR RECEIVER
FCR BIT-0 = 0
(FIFO DISABLED)
FCR BIT-0 = 1
(FIFO ENABLED)
INTA/B Pin
LOW = No data
HIGH = 1 byte
LOW = FIFO below trigger level
HIGH = FIFO above trigger level
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