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Chapter 8
DMA Controller (DMAC)
Preliminary User’s Manual U17566EE1V2UM00
Figure 8-8
shows a single transfer mode example in which two or more lower
priority DMA transfer requests are generated within one clock after the end of a
single transfer. DMA channels 0, 2 and 3 are used for this single transfer
example. When three or more DMA transfer request signals are activated at
the same time always the two highest priority DMA transfers are performed
alternately.
Figure 8-8
Single transfer example 4
Note
The bus is always released
8.12.2
Block transfer mode
In the block transfer mode, once transfer begins, the DMAC continues the
transfer operation without releasing the bus until a terminal count occurs. No
other DMA requests are acknowledged during block transfer.
After the block transfer ends and the DMAC releases the bus and another DMA
transfer can be acknowledged.
Figure 8-9
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 the block transfer example.
Figure 8-9
Block transfer example
DMA2 CPU
DMA3
CPU
CPU
DMA3 CPU
CPU
DMA2
DMA0
CPU
DMA0
Note
Note
Note
Note
Note
DMA2 CPU
Note
DMA3
CPU
DMA2 CPU
CPU
DMA3
Note
CPU
CPU
Note
Note
DMA Transfer
Request CH0
DMA Transfer
Request CH2
DMA Transfer
Request CH3
DMA channel 0
terminal count
DMA channel 2
terminal count
DMA channel 3
terminal count
DMA Transfer
Request CH2
DMA Transfer
Request CH3
DMA channel 3
terminal count
DMA3
CPU
DMA3
DMA2 DMA2 DMA2
CPU
CPU
CPU
DMA3 DMA3
DMA3
DMA3
DMA3 DMA3
DMA2 DMA2
The bus is always released
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