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CHAPTER 11 DMAAU (DMA ADDRESS UNIT)
This chapter describes the DMAAU register’s operations and settings.
11.1 GENERAL
The DMAAU register controls the DMA addresses for the AIU and IrDA 4-Mbps communication module (FIR).
The DMA channel used for each unit can set a DMA start address as any half-word address in the space from
0x0000 0000 to 0x01FF FFFE, and is retained in DRAM as a 2-Kbyte block that starts at the address which is
generated by masking the low-order 10 bits of the DMA start address.
After a DMA start address is set to the DMA base address register, the V
R
4102 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 V
R
4102 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 V
R
4102 adds 1 Kbyte 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 V
R
4102 writes the contents of the DMA base
address register to the DMA address register and continues the DMA transfer.
4. The V
R
4102 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 V
R
4102 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 V
R
4102 subtracts 1 Kbyte 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 V
R
4102 writes the contents of the DMA base
address register to the DMA address register and continues the DMA transfer.
4. The V
R
4102 repeats 2. and 3. until all the data is transferred.
Figure 11-1. DMA Space Used in DMA Transfers
Second page
First page boundary
Base address
o
DMA space address
Second page
First page boundary
Base address
o
DMA space address
(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
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3
5
7
2
4
6
8
2
4
6
8
1
3
5
7
Caution
DMA operations are not guaranteed if an address overlaps with another DMA buffer.