Freescale Semiconductor MSC8156 Evaluation Module MSC8156EVM MSC8156EVM Benutzerhandbuch
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MSC8156EVM
MSC8156 Reference Manual, Rev. 2
14-28
Freescale Semiconductor
Direct Memory Access (DMA) Controller
14.7.1
DMA Buffer Descriptor Base Registers x (DMABDBRx)
Each DMABDBRx holds the user-programmable addresses of the BD tables for DMA channel x.
There are two fields: BDTPTR that identifies the base address of the Buffer Descriptor Table and
DESO field that identifies the location offset for the destination buffer within the table. All the
channel properties should be programmed, including the relevant BD, before the channel is
enabled. For more information on BD address calculation, see the discussion in
Section 14.7.22, DMA Channel Buffer Descriptors, on page 14-45.
There are two fields: BDTPTR that identifies the base address of the Buffer Descriptor Table and
DESO field that identifies the location offset for the destination buffer within the table. All the
channel properties should be programmed, including the relevant BD, before the channel is
enabled. For more information on BD address calculation, see the discussion in
Section 14.7.22, DMA Channel Buffer Descriptors, on page 14-45.
DMABDBR[0–15]
DMA Buffer Descriptor Base Registers 0–15
Offset 0x000 + x*0x4
Bit
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
—
BDTPTR
Type
R/W
Reset
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
Bit
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
BDTPTR
DESO
Type
R/W
Reset
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
Table 14-15. DMABDBRx Field Descriptions
Bits
Reset
Description
Setting
—
31–28
0
Reserved. Write to zero for future compatibility.
BDTPTR
27–4
0
Buffer Descriptor Table Pointer
Holds the 24 most significant bits, out of the 32
bit Buffer Descriptors Table (BDT) address.
Holds the 24 most significant bits, out of the 32
bit Buffer Descriptors Table (BDT) address.
DESO
3–0
0
Destination Offset
Holds the offset of destination buffer descriptor
table from the BTD base (BDTPTR
Holds the offset of destination buffer descriptor
table from the BTD base (BDTPTR
×
256).
0000
Destination table offset is 0x20.
0001
Destination table offset is 0x40.
0010 Destination table offset is 0x80.
0011 Destination table offset is 0x100.
0100 Destination table offset is 0x200.
0101 Destination table offset is 0x400.
0110 Destination table offset is 0x600.
0111
Destination table offset is 0x800.
1000 Destination table offset is 0x1000.
1001 Destination table offset is 0x2000.
1010 Destination table offset is 0x3000.
1011 Destination table offset is 0x4000.
11xx Reserved.