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UM10360_0
© NXP B.V. 2009. All rights reserved.
User manual
Rev. 00.06 — 5 June 2009
577 of 808
NXP Semiconductors
UM10360
Chapter 31: LPC17xx General Purpose DMA (GPDMA) controller
has processed the value read, the channel may have advanced. It is intended to be read
only when a channel has stopped.
shows the bit assignments of the
DMACCxControl Register.
5.20.1 Protection and access information
AHB access information is provided to the source and destination peripherals when a
transfer occurs. The transfer information is provided by programming the DMA channel
(the Prot bits of the DMACCxControl Register, and the Lock bit of the DMACCxConfig
Register). These bits are programmed by software. Peripherals can use this information if
necessary. Three bits of information are provided, and are used as shown in
Table 545. DMA channel control registers (DMACCxControl - 0x5000 41xC)
Bit
Name
Function
11:0
TransferSize
Transfer size. This field sets the size of the transfer. The transfer size value must be
set before the channel is enabled. Transfer size is updated as data transfers are
completed.
A read from this field indicates the number of transfers completed on the destination
bus. Reading the register when the channel is active does not give useful information
because by the time that the software has processed the value read, the channel
might have progressed. It is intended to be used only when a channel is enabled and
then disabled.
14:12
SBSize
Source burst size. Indicates the number of transfers that make up a source burst.
This value must be set to the burst size of the source peripheral, or if the source is
memory, to the memory boundary size. The burst size is the amount of data that is
transferred when the DMACBREQ signal goes active in the source peripheral.
000 - 1
001 - 4
010 - 8
011 - 16
100 - 32
101 - 64
110 - 128
111 - 256
17:15
DBSize
Destination burst size. Indicates the number of transfers that make up a destination
burst transfer request. This value must be set to the burst size of the destination
peripheral or, if the destination is memory, to the memory boundary size. The burst
size is the amount of data that is transferred when the DMACBREQ signal goes
active in the destination peripheral.
000 - 1
001 - 4
010 - 8
011 - 16
100 - 32
101 - 64
110 - 128
111 - 256