NXP Semiconductors LPC24XX UM10237 - Manual (Page 737)

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User manual Rev. 04 — 26 August 2009 737 of 792
NXP Semiconductors
UM10237
Chapter 32: LPC24XX General Purpose DMA (GPDMA) controller
10.1 Peripheral-to-memory, or Memory-to-peripheral DMA flow
For a peripheral-to-memory or memory-to-peripheral DMA flow the following sequence
occurs:
1. Program and enable the DMA channel.
2. Wait for a DMA request.
3. The GPDMA starts transferring data when:
– The DMA request goes active.
– The DMA stream has the highest pending priority.
– The GPDMA is the bus master of the AHB bus.
4. If an error occurs while transferring the data, an error interrupt is generated and
disables the DMA stream, and the flow sequence ends.
5. Decrement the transfer count if the GPDMA is performing the flow control.
6. If the transfer has completed (indicated by the transfer count reaching 0 if the GPDMA
is performing flow control, or by the peripheral sending a DMA request if the
peripheral is performing flow control):
– The GPDMA responds with a DMA acknowledge.
– The terminal count interrupt is generated (this interrupt can be masked).
– If the DMACCxLLI Register is not 0, then reload the DMACCxSrcAddr,
DMACCxDestAddr, DMACCxLLI, and DMACCxControl Registers and go back to
step 2. However, if DMACCxLLI is 0, the DMA stream is disabled and the flow
sequence ends.
See Section 32–4.1 for memory regions accessible by the GPDMA.
10.2 Peripheral-to-peripheral DMA flow
For a peripheral-to-peripheral DMA flow the following sequence occurs:
1. Program and enable the DMA channel.
2. Wait for a source DMA request.
3. The GPDMA starts transferring data when:
Table 676. DMA request signal usage
Transfer Direction Request Generator Flow Controller
Memory-to-peripheral Peripheral GPDMA
Memory-to-peripheral Peripheral Peripheral
Peripheral-to-memory Peripheral GPDMA
Peripheral-to-memory Peripheral Peripheral
Memory-to-memory GPDMA GPDMA
Source peripheral to destination
peripheral Source peripheral and
destination peripheral Source peripheral
Source peripheral to destination
peripheral Source peripheral and
destination peripheral Destination peripheral
Source peripheral to destination
peripheral Source peripheral and
destination peripheral GPDMA