
User’s Manual U14579EJ2V0UM
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CHAPTER 4 DMAAU (DMA ADDRESS UNIT)
4.1
General
The DMAAU register controls the DMA addresses for the AIU.
The DMA channel used for each unit can set a DMA start address as any half-word address in the physical
address from 0x0000 0000 to 0xFFFF FFFE, and is retained in DRAM as a 2 KB block that starts at the address
which is generated by masking the lower 10 bits of the DMA start address.
Caution
DMA operations are not guaranteed if an address overlaps with another DMA buffer.
After a DMA start address is set to the DMA base address register, the VRC4173 performs DMA transfer using the
registers of DMAAU as below.
(1) When the DMA start address is included in the first page of the DMA space
<1> The VRC4173 starts a DMA transfer after writing the start address to the DMA address register.
<2> When the DMA transfer reaches the first page boundary, the VRC4173 adds 1 KB to the contents of the DMA
base address register, writes the value to the DMA address register, and continues the DMA transfer.
<3> When the DMA transfer reaches the second page boundary, the VRC4173 writes the contents of the DMA
base address register to the DMA address register and continues the DMA transfer.
<4> The VRC4173 repeats <2> and <3> until all the data is transferred.
(2) When the DMA start address is included in the second page of the DMA space
<1> The VRC4173 starts a DMA transfer after writing the start address to the DMA address register.
<2> When the DMA transfer reaches the second page boundary, the VRC4173 subtracts 1 KB from the contents
of the DMA base address register, writes the value to the DMA address register, and continues the DMA
transfer.
<3> When the DMA transfer reaches the first page boundary, the VRC4173 writes the contents of the DMA base
address register to the DMA address register and continues the DMA transfer.
<4> The VRC4173 repeats <2> and <3> until all the data is transferred.
Figure 4-1. DMA Space Used in DMA Transfers
Second page boundary
First page boundary
Base address
→
DMA space address
First page boundary
Base address
→
DMA space address
<2>
<8>
<6>
<4>
<2>
<8>
<6>
<4>
<1>
<7>
<5>
<3>
<1>
<7>
<5>
<3>
(a) When the DMA start address is included
in the first page of the DMA space
(b) When the DMA start address is included
in the second page of the DMA space