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14.5
On-Demand Data Transfer Mode
14.5.1
Operation
Setting the DDT bit to 1 in DMAOR causes a transition to on-demand data transfer mode (DDT
mode). In DDT mode, it is possible to specify direct single address mode transfer to channel 0 via
the data bus and DDT module, and simultaneously issue a transfer request, using the '%5(4,
%$9/, 75, 7'$&., and ID [1:0] signals between an external device and the DMAC. Figure
14.23 shows a block diagram of the DMAC, DDT, BU, and an external device (with '%5(4,
%$9/, 75, 7'$&., ID [1:0], and D [63:0] = DTR pins).
DMAC
SAR0
DAR0
DMATCR0
CHCR0
DREQ0–3
ddtmode tdack id[1:0]
BSC
Data buffer
Figure 14.23 On-Demand Transfer Mode Block Diagram
For channels 1 to 3, after making the settings for normal DMA transfer using the CPU, a transfer
request can be issued from an external device using the '%5(4, %$9/, 75, 7'$&., ID [1:0],
and D [63:0] = DTR signals (handshake protocol using the data bus). A transfer request can also
be issued simply by asserting 75, without using the external bus (handshake protocol without use
of the data bus). For channel 2, after making the DMA transfer settings in the normal way, a
transfer request can be issued directly from an external device (with '%5(4, %$9/, 75,
7'$&., ID [1:0], and D [63:0] = DTR pins) by asserting '%5(4 and 75 simultaneously.
Note: DTR format = Data transfer request format
In DDT mode, there is a choice of five modes for performing DMA transfer.
Rev. 4.0, 04/00, page 474 of 850
DDT
Data
buffer
Request
controller
ddtmode
bavl
ID[1:0]
Memory
External
device (with
DTR
,
,
,
and ID [1:0])
FIFO or
memory
,
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