CHAPTER 7 DMAC
Preliminary User’s Manual A14874EJ3V0UM
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7.8.4 Block transfer mode
In block transfer mode, once transfer begins, the transfers continue without releasing the bus until a terminal count
occurs. No other DMA transfer requests are acknowledged during a block transfer.
After the block transfer ends and the DMAC has released the bus, another DMA transfer can be acknowledged.
Although it is prohibited to insert a CPU bus cycle during a block transfer, bus mastership can be transferred even
during a block transfer in response to a request by the external bus master (including SDRAM refresh).
Figure 7-22 shows a block transfer mode example. It is a block transfer mode example in which a higher priority
DMA transfer request is generated. DMA channels 2 and 3 are used for a block transfer.
Figure 7-22. Block Transfer Example
DMA3
CPU
DMA3
DMA2 DMA2 DMA2
CPU
CPU
CPU
DMA3 DMA3
DMA3
DMA3
DMA3 DMA3
DMARQ3
(Input)
DMA2 DMA2
DMA channel 3 terminal count
DMARQ2
(Input)
The bus is always released