Datasheet

V850ES/JG3 CHAPTER 18 DMA FUNCTION (DMA CONTROLLER)
R01UH0015EJ0300 Rev.3.00 Page 616 of 870
Sep 30, 2010
(3) DMA transfer count registers 0 to 3 (DBC0 to DBC3)
The DBC0 to DBC3 registers are 16-bit registers that set the byte transfer count for DMA channel n (n = 0 to 3).
These registers hold the remaining transfer count during DMA transfer.
These registers are decremented by 1 per one transfer regardless of the transfer data unit (8/16 bits), and the
transfer is terminated if a borrow occurs.
These registers can be read or written in 16-bit units.
Byte transfer count 1 or remaining byte transfer count
Byte transfer count 2 or remaining byte transfer count
:
Byte transfer count 65,536 (2
16
) or remaining byte transfer count
BC15 to
BC0
0000H
0001H
:
FFFFH
Byte transfer count setting or remaining
byte transfer count during DMA transfer
After reset: Undefined R/W Address: DBC0 FFFFF0C0H, DBC1 FFFFF0C2H,
DBC2 FFFFF0C4H, DBC3 FFFFF0C6H
DBCn
(n = 0 to 3)
15
BC15
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
BC0
The number of transfer data set first is held when DMA transfer is complete.
Cautions 1. Set the DBCn register at the following timing when DMA transfer is disabled (DCHCn.Enn
bit = 0).
• Period from after reset to start of first DMA transfer
• Period from after channel initialization by DCHCn.INITn bit to start of DMA transfer
• Period from after completion of DMA transfer (DCHCn.TCn bit = 1) to start of the next
DMA transfer
2. Following reset, set the DSAnH, DSAnL, DDAnH, DDAnL, and DBCn registers before
starting DMA transfer. If these registers are not set, the operation when DMA transfer is
started is not guaranteed.