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UM10360_0
© NXP B.V. 2009. All rights reserved.
User manual
Rev. 00.06 — 5 June 2009
580 of 808
NXP Semiconductors
UM10360
Chapter 31: LPC17xx General Purpose DMA (GPDMA) controller
5.21.1 Lock control
The lock control may set the lock bit by writing a 1 to bit 16 of the DMACCxConfig
Register. When a burst occurs, the AHB arbiter will not de-grant the master during the
burst until the lock is de-asserted. The DMA Controller can be locked for a a single burst
such as a long source fetch burst or a long destination drain burst. The DMA Controller
does not usually assert the lock continuously for a source fetch burst followed by a
destination drain burst.
There are situations when the DMA Controller asserts the lock for source transfers
followed by destination transfers. This is possible when internal conditions in the DMA
Controller permit it to perform a source fetch followed by a destination drain back-to-back.
5.21.2 Transfer type
lists the bit values of the transfer type bits identified in
6.
Using the DMA controller
6.1 Programming the DMA controller
All accesses to the DMA Controller internal register must be word (32-bit) reads and
writes.
6.1.1 Enabling the DMA controller
To enable the DMA controller set the Enable bit in the DMACConfig register.
6.1.2 Disabling the DMA controller
To disable the DMA controller:
•
Read the DMACEnbldChns register and ensure that all the DMA channels have been
disabled. If any channels are active, see Disabling a DMA channel.
•
Disable the DMA controller by writing 0 to the DMA Enable bit in the DMACConfig
register.
6.1.3 Enabling a DMA channel
To enable the DMA channel set the channel enable bit in the relevant DMA channel
configuration register. Note that the channel must be fully initialized before it is enabled.
6.1.4 Disabling a DMA channel
A DMA channel can be disabled in three ways:
Table 547. Transfer type bits
Bit value
Transfer type
Controller
000
Memory to memory
DMA
001
Memory to peripheral
DMA
010
Peripheral to memory
DMA
011
Source peripheral to destination peripheral
DMA
100 to 111
Reserved, do not use these combinations
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