CHAPTER 6 DMA FUNCTIONS (DMA CONTROLLER)
User’s Manual U12688EJ4V0UM00
179
6.5
Transfer Mode
6.5.1 Single transfer mode
In single transfer mode, the DMAC releases the bus at each byte/halfword transfer. If there is a subsequent DMA
transfer request, transfer is performed again. This operation 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.
Figures 6-2 and 6-3 show examples of single transfer. Figure 6-3 shows an example of single transfer in which a
higher priority DMA request is issued. DMA channels 0 to 2 are in block transfer mode and channel 3 is in single
transfer mode.
Figure 6-2. Single Transfer Example 1
CPU
DMARQ3
CPU DMA3 CPU DMA3 CPU DMA3 CPU CPU CPU CPU CPU CPU DMA3 CPU DMA3 CPU CPU CPU
DMA channel 3 terminal count
Figure 6-3. Single Transfer Example 2
CPU CPU CPU DMA3 CPU DMA0 DMA0 CPU DMA1 DMA1 CPU DMA2 DMA2 CPU DMA3 CPU DMA3
DMARQ3
DMARQ2
DMARQ1
DMARQ0
DMA channel 3
terminal count
DMA channel 0
terminal count
DMA channel 2
terminal count
Note
Note
Note
Note
DMA channel 1
terminal count
Note The bus is always released.
Содержание V850E/MS1 UPD703100
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