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Chapter 7
DMA Functions (DMA Controller)
Preliminary User’s Manual U15839EE1V0UM00
7.2.3 DMA transfer count registers 0 to 3 (DBC0 to DBC3)
These 16-bit registers are used to set the transfer counts for DMA channels n. They store the remaining
transfer counts during DMA transfer.
Since these registers are configured as 2-stage FIFO buffer registers, a new DMA transfer count for
DMA transfer can be specified during DMA transfer (refer to 7.3 Next Address Setting Function).
During DMA transfer these registers are decremented by 1 for each transfer that is performed. DMA
transfer is terminated when an underflow occurs (from 0 to FFFFH). On terminal count these registers
are rewritten with the value that was set immediately before.
These registers can be read/written in 16-bit units.
Figure 7-5:
DMA Transfer Count Registers 0 to 3 (DBC0 to DBC3)
Cautions: 1. In case of a line transfer and the setting of the DBCn register is 0003H (four trans-
fers), one line transfer is applied.
2. For a setting of the DBCn register in which the transfer count cannot be divided
by 4, the sections that can be line transferred are (line) transferred first, then the
remaining indivisible sections are transferred as single transfer.
Remark:
n = 0 to 3
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
Address
Initial
value
DBC0
BC15 BC14 BC13 BC12 BC11 BC10 BC9 BC8 BC7 BC6 BC5 BC4 BC3 B2C BC1 BC0 FFFFF0C0H undef.
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
Address
Initial
value
DBC1
BC15 BC14 BC13 BC12 BC11 BC10 BC9 BC8 BC7 BC6 BC5 BC4 BC3 B2C BC1 BC0 FFFFF0C2H undef.
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
Address
Initial
value
DBC2
BC15 BC14 BC13 BC12 BC11 BC10 BC9 BC8 BC7 BC6 BC5 BC4 BC3 B2C BC1 BC0 FFFFF0C4H undef.
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
Address
Initial
value
DBC3
BC15 BC14 BC13 BC12 BC11 BC10 BC9 BC8 BC7 BC6 BC5 BC4 BC3 B2C BC1 BC0 FFFFF0C6H undef.
Bit Position
Bit Name
Function
15 to 0
BC15 to
BC0
Sets the transfer count. It stores the remaining transfer count during DMA transfer.
DBCn
States
0000H
Transfer count 1 or remaining transfer count
0001H
Transfer count 2 or remaining transfer count
:
:
FFFFH
Transfer count 65,536 (2
16
) or remaining transfer count
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