CHAPTER 7 DMAC
Preliminary User’s Manual A14874EJ3V0UM
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7.8.2 Single-step transfer mode
In single-step transfer mode, the DMAC releases the bus after each byte, halfword, or word transfer. Once a DMA
transfer request signal (DMARQ3 to DMARQ0) is received, this operation continues until a terminal count occurs.
If a higher priority DMA transfer request is generated while the DMAC has released the bus, the higher priority
DMA transfer request always takes precedence.
Figures 7-16 and 7-17 show single-step transfer mode examples.
Figure 7-16. Single-Step Transfer Example 1
DMA1
CPU
CPU
CPU
CPU
CPU
CPU
CPU
CPU
DMA1
CPU
CPU
DMA1
DMA1
CPU
DMARQ1
(Input)
CPU
CPU
DMA channel 1 terminal count
Note
Note
Note
Note
The bus is always released.
Figure 7-17. Single-Step Transfer Example 2
DMA0
DMA0
CPU
CPU
DMA1 CPU
CPU
CPU
CPU
DMA1
CPU
CPU
DMA1
DMA0
CPU
DMARQ1
(Input)
DMA1 CPU
DMARQ0
(Input)
DMA channel 0
terminal count
DMA channel 1
terminal count
Note
Note
Note
Note
Note
Note
Note
The bus is always released.