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UM10503
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© NXP B.V. 2015. All rights reserved.
User manual
Rev. 2.1 — 10 December 2015
1162 of 1441
NXP Semiconductors
UM10503
Chapter 41: LPC43xx/LPC43Sxx UART1
41.6.6.1 DMA Operation
The user can optionally operate the UART transmit and/or receive using DMA. The DMA
mode is determined by the DMA Mode Select bit in the FCR register. Note that for DMA
operation as for any operation of the UART, the FIFOs must be enabled via the FIFO
Enable bit in the FCR register.
UART receiver DMA
In DMA mode, the receiver DMA request is asserted on the event of the receiver FIFO
level becoming equal to or greater than trigger level, or if a character time-out occurs. See
the description of the RX Trigger Level above. The receiver DMA request is cleared by the
DMA controller.
UART transmitter DMA
In DMA mode, the transmitter DMA request is asserted on the event of the transmitter
FIFO transitioning to not full. The transmitter DMA request is cleared by the DMA
controller.
41.6.7 UART1 Line Control Register
The LCR determines the format of the data character that is to be transmitted or received.
1
RXFIFORES
RX FIFO Reset.
0
0
No effect. No impact on either of UART1 FIFOs.
1
Clear. Writing a logic 1 to FCR[1] will clear all bytes in UART1 Rx FIFO, reset
the pointer logic. This bit is self-clearing.
2
TXFIFORES
TX FIFO Reset.
0
0
No effect. No impact on either of UART1 FIFOs.
1
Clear. Writing a logic 1 to FCR[2] will clear all bytes in UART1 TX FIFO, reset
the pointer logic. This bit is self-clearing.
3
DMAMODE
DMA Mode Select. When the FIFO enable bit (bit 0 of this register) is set, this
bit selects the DMA mode. See
0
5:4
-
Reserved, user software should not write ones to reserved bits. The value read
from a reserved bit is not defined.
NA
7:6
RXTRIGLVL
RX Trigger Level. These two bits determine how many receiver UART1 FIFO
characters must be written before an interrupt is activated.
0
0x0
Level 0. Trigger level 0 (1 character or 0x01).
0x1
Level 1. Trigger level 1 (4 characters or 0x04).
0x2
Level 2. Trigger level 2 (8 characters or 0x08).
0x3
Level 3. Trigger level 3 (14 characters or 0x0E).
31:8
-
Reserved, user software should not write ones to reserved bits.
NA
Table 959: UART1 FIFO Control Register (FCR, address 0x4008 2008) bit description
Bit
Symbol
Value
Description
Reset
value