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UM10316_0
© NXP B.V. 2008. All rights reserved.
User manual
Rev. 00.06 — 17 December 2008
517 of 571
NXP Semiconductors
UM10316
Chapter 30: LPC29xx General Purpose DMA (GPDMA) controller
4.1.7 Channel hardware
Each stream is supported by a dedicated hardware channel, including source and
destination controllers, as well as a FIFO. This enables better latency than a DMA
controller with only a single hardware channel shared between several DMA streams and
simplifies the control logic.
4.1.8 DMA request priority
DMA channel priority is fixed. DMA channel 0 has the highest priority and DMA channel 7
has the lowest priority.
If the DMA Controller is transferring data for the lower priority channel and then the higher
priority channel goes active, it completes the number of transfers delegated to the master
interface by the lower priority channel before switching over to transfer data for the higher
priority channel. In the worst case this is as large as a one quadword.
It is recommended that memory-to-memory transactions use the lowest priority channel.
Otherwise other AHB bus masters are prevented from accessing the bus during DMA
Controller memory-to-memory transfer.
4.1.9 Interrupt generation
A combined interrupt output is generated as an OR function of the individual interrupt
requests of the DMA Controller and is connected to the interrupt controller.
4.2 DMA system connections
The connection of the DMA Controller to supported peripheral devices is shown in
In addition to the UART and SPI peripherals, the GPIOs, the WDT, and the timers can be
accessed by the GPDMA as a memory-to-memory transaction with no flow control.
Table 444. Peripheral connections to the DMA controller and matching flow control signals
Peripheral
Number
DMA Slave
DMACBREQ DMACSREQ
0
SPI0 transmit
x
x
1
SPI0 receive
x
x
2
SPI1 transmit
x
x
3
SPI1 receive
x
x
4
SPI2 transmit
x
x
5
SPI2 receive
x
x
6
UART0 transmit
x
-
7
UART0 receive
x
-
8
UART1 transmit
x
-
9
UART1 receive
x
-
15:10
reserved
-
-