CHAPTER 6 DMA FUNCTIONS (DMA CONTROLLER)
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User’s Manual U15195EJ5V0UD
6.3.3 DMA transfer count registers 0 to 3 (DBC0 to DBC3)
These 16-bit registers are used to set the byte transfer counts for DMA channels n (n = 0 to 3). They store the
remaining transfer counts during DMA transfer.
Since these registers are configured as 2-stage FIFO buffer registers, a new DMA byte transfer count for DMA
transfer can be specified during DMA transfer. (Refer to
6.8 Next Address Setting Function
.) In this case, if a new
DBCn register is set, the value set will be transferred to the slave register and enabled only if DMA transfer ends
normally, and the TCn bit of DMA channel control register n (DCHCn) has been set to 1 or the INITn bit of the DCHCn
register has been set to 1 (n = 0 to 3).
These registers are decremented by 1 per transfer. Transfer is terminated if a borrow occurs.
These registers can be read/written in 16-bit units.
Cautions 1. During 2-cycle transfer when the transfer source is the internal RAM, do not set the transfer
count to 2 (the set value of the DBCn register is 0001H).
If DMA transfer is required twice, perform DMA transfer with the transfer count set to one (the
set value of the DBCn register is 0000H) twice.
2. Do not set the DBCn register while DMA is suspended.
Remark
If the DBCn register is read after a terminal count has occurred during DMA transfer without the value
of the DBCn register rewritten, the value set immediately before DMA transfer is read (0000H is not
read even after completion of transfer).
15
BC15
DBC0
Address
FFFFF0C0H
After reset
Undefined
14
BC14
13
BC13
12
BC12
11
BC11
10
BC10
9
BC9
8
BC8
7
BC7
6
BC6
5
BC5
4
BC4
3
BC3
2
BC2
1
BC1
0
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
BC0
BC15
DBC1
Address
FFFFF0C2H
After reset
Undefined
BC14 BC13 BC12 BC11 BC10 BC9 BC8 BC7 BC6 BC5 BC4 BC3 BC2 BC1 BC0
BC15
DBC2
Address
FFFFF0C4H
After reset
Undefined
BC14 BC13 BC12 BC11 BC10 BC9 BC8 BC7 BC6 BC5 BC4 BC3 BC2 BC1 BC0
BC15
DBC3
Address
FFFFF0C6H
After reset
Undefined
BC14 BC13 BC12 BC11 BC10 BC9 BC8 BC7 BC6 BC5 BC4 BC3 BC2 BC1 BC0
Bit position
Bit name
Function
Sets the byte transfer count. It stores the remaining byte transfer count during DMA
transfer.
DBCn (n = 0 to 3)
States
0000H
Byte transfer count 1 or remaining byte transfer count
0001H
Byte transfer count 2 or remaining byte transfer count
:
:
FFFFH
Byte transfer count 65,536 (2
16
) or remaining byte transfer
count
15 to 0
BC15 to BC0
Содержание PD703114
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