UM10360 All information provided in this document is subject to legal disclaimers. © NXP B.V. 2013. All rights reserved.
User manual Rev. 3 — 19 December 2013 611 of 841
NXP Semiconductors
UM10360
Chapter 31: LPC176x/5x General Purpose DMA (GPDMA)
7. When the destination DMA request goes active and there is data in the DMA
Controller FIFO, transfer data into the destination peripheral.
8. If an error occurs while transferring the data, an error interrupt is generated, the DMA
stream is disabled, and the flow sequence ends.
9. If the transfer has completed it is indicated by the transfer count reaching 0. The
following happens:
– The DMA Controller responds with a DMA acknowledge to the destination
peripheral.
– 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 to back
to step 2. However, if DMACCxLLI is 0, the DMA stream is disabled and the flow
sequence ends.
31.6.2.3 Memory-to-memory DMA flow
For a memory-to-memory DMA flow the following sequence occurs:
1. Program and enable the DMA channel.
2. Transfer data whenever the DMA channel has the highest pending priority and the
DMA Controller gains mastership of the AHB bus.
3. If an error occurs while transferring the data, generate an error interrupt and disable
the DMA stream.
4. Decrement the transfer count.
5. If the count has reached zero:
– Generate a terminal count interrupt (the interrupt can be masked).
– If the DMACCxLLI Register is not 0, then reload the DMACCxSrcAddr,
DMACCxDestAddr, DMACCxLLI, and DMACCxControl Registers and go to back
to step 2. However, if DMACCxLLI is 0, the DMA stream is disabled and the flow
sequence ends.
Note: Memory-to-memory transfers should be programmed with a low channel priority,
otherwise other DMA channels cannot access the bus until the memory-to-memory
transfer has finished, or other AHB masters cannot perform any transaction.
31.6.3 Interrupt requests
Interrupt requests can be generated when an AHB error is encountered or at the end of a
transfer (terminal count), after all the data corresponding to the current LLI has been
transferred to the destination. The interrupts can be masked by programming bits in the
relevant DMACCxControl and DMACCxConfig Channel Registers. The interrupt requests
from all DMA channels can be found in the DMACRawIntTCStat and DMACRawIntErrStat
registers. The masked versions of the DMA interrupt data is contained in the
DMACIntTCStat and DMACIntErrStat registers. The DMACIntStat register then combines
the DMACIntTCStat and DMACIntErrStat requests into a single register to enable the
source of an interrupt to be found quickly. Writing to the DMACIntTCClear or the
DMACIntErrClr Registers with a bit set to 1 enables selective clearing of interrupts.
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