CHAPTER 6 DMA FUNCTIONS (DMA CONTROLLER)
User’s Manual U12688EJ4V0UM00
167
6.3.3 DMA byte count registers 0 to 3 (DBC0 to DBC3)
These 16-bit registers are used to set the byte transfer counts for DMA channel n (n = 0 to 3).
They store the remaining transfer counts during DMA transfer.
These registers are decremented by 1 for byte transfer and by two for 16-bit transfer. Transfer ends when a
borrow occurs. Thus, “transfer count –1” should be set for byte transfer and “(transfer count –1)
×
2” for 16-bit
transfer.
These registers can be read/written in 16-bit units.
0
BC
0
Address
FFFFF1E0H
After reset
Undefined
1
BC
1
2
BC
2
3
BC
3
4
BC
4
5
BC
5
6
BC
6
7
BC
7
8
BC
8
9
BC
9
10
11
12
13
14
15
DBC0
FFFFF1E2H
Undefined
DBC1
FFFFF1E4H
Undefined
DBC2
FFFFF1E6H
Undefined
BC
10
BC
11
BC
12
BC
13
BC
14
BC
15
BC
0
BC
1
BC
2
BC
3
BC
4
BC
5
BC
6
BC
7
BC
8
BC
9
BC
10
BC
11
BC
12
BC
13
BC
14
BC
15
BC
0
BC
1
BC
2
BC
3
BC
4
BC
5
BC
6
BC
7
BC
8
BC
9
BC
10
BC
11
BC
12
BC
13
BC
14
BC
15
BC
0
BC
1
BC
2
BC
3
BC
4
BC
5
BC
6
BC
7
BC
8
BC
9
BC
10
BC
11
BC
12
BC
13
BC
14
BC
15
DBC3
Bit Position
Bit Name
Function
Byte Count
Sets the byte transfer count. During DMA transfer, it stores the remaining byte transfer
count.
DBCn
States
0000H
Byte transfer count 1 or the remaining byte transfer count
0001H
Byte transfer count 2 or the remaining byte transfer count
:
:
FFFFH
Byte transfer count 65,536 (2
16
) or the remaining byte transfer count
15 to 0
BC15 to
BC0
Remark
n = 0 to 3
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