CHAPTER 13 DMA FUNCTIONS
User’s Manual U15109EJ3V0UD
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475
(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 DMA transfer.
The transfer count is decremented by 1 per transfer if the transfer is a byte (8-bit) transfer, and by 2 per transfer if
the transfer is a 16-bit transfer. Transfer ends 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 can be read/written in 8-bit units.
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.
(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
(6) Start factor settings
(n = 0 to 5).
This register can be read/written in 8- or 1-bit units.
After reset:
00H
R/W
Address: FFFFF38EH
7
6
5
4
3
2
1
0
DMAS
0
0
0
0
0
DMAS2
DMAS1
DMAS0