CHAPTER 12 DMA FUNCTIONS
User’s Manual U13850EJ4V0UM
366
12.3.3 DMA byte count registers 0 to 5 (DBC0 to DBC5)
These are 8-bit registers that are used to set the number of transfers for DMA channel n.
The remaining number of transfers is retained during the DMA transfers.
A value of 1 is decremented once per transfer if the transfer is a byte (8-bit) transfer, and a value of 2 is
decremented once per transfer if the transfer is a 16-bit transfer. The transfers are ended when a borrow operation
occurs. Accordingly, “number of transfers
−
1” should be set for byte (8-bit) transfers and “(number of transfers
−
1)
×
2” should be set for 16-bit transfers.
These registers are can be read/written in 8-bit units.
Figure 12-7. Format of DMA Byte Count Registers 0 to 5 (DBC0 to DBC5)
After reset: Undefined
R/W
Address: DBC0
FFFFF184H
DBC3
FFFFF1B4H
DBC1
FFFFF194H
DBC4
FFFFF1C4H
DBC2
FFFFF1A4H
DBC5
FFFFF1D4H
7
6
5
4
3
2
1
0
DBCn
BCn7
BCn6
BCn5
BCn4
BCn3
BCn2
BCn1
BCn0
(n = 0 to 5)
Caution Values set to bit 0 are ignored during 16-bit transfers.
12.3.4 DMA start factor expansion register (DMAS)
This is an 8-bit register for expanding the factors that start DMA.
The DMA start factor is decided according to the combination of TTYPn1 and TTYPn0 of the DCHCn register.
For setting bits DMAS2 to DMAS0, refer to
12.3.5 DMA channel control registers 0 to 5 (DCHC0 to DCHC5)
(n = 0 to 5).
This register can be read/written in 8/1-bit units.
Figure 12-8. DMA Start Factor Expansion Register (DMAS)
After reset: 00H
R/W
Address: FFFFF38EH
7
6
5
4
3
2
1
0
DMAS
0
0
0
0
0
DMAS2
DMAS1
DMAS0
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