CHAPTER 6 DMA FUNCTIONS (DMA CONTROLLER)
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User’s Manual U15195EJ5V0UD
6.4.2 Single-step transfer mode
In single-step transfer mode, the DMAC releases the bus at each byte/halfword transfer. Once a DMA transfer
request signal has been received, transfer continues until a terminal count occurs.
When the DMAC has released the bus, if another higher priority DMA transfer request is issued, the higher priority
DMA request always takes precedence.
The following shows examples of single-step transfer. Figure 6-6 shows a single-step transfer mode example in
which a higher priority DMA transfer request is generated and DMA channels 0 and 1 are set to the single-step
transfer mode.
Figure 6-5. Single-Step Transfer Example 1
DMA1
CPU
CPU
CPU
CPU
CPU
CPU
CPU
CPU
DMA1
CPU
CPU
DMA1
DMA1
CPU
DMARQ1
CPU
CPU
DMA channel 1
terminal count
Note
Note
Note
(Internal signal)
Note
The bus is always released.
Figure 6-6. Single-Step Transfer Example 2
DMA0
DMA0
CPU
CPU
DMA1 CPU
CPU
CPU
CPU
DMA1
CPU
CPU
DMA1
DMA0
CPU
DMARQ1
DMA1 CPU
DMARQ0
DMA channel 0
terminal count
DMA channel 1
terminal count
Note
Note
Note
Note
Note
Note
(Internal signal)
(Internal signal)
Note
The bus is always released.