Intel
®
81341 and 81342 I/O Processors
December 2007
Developer’s Manual
Order Number: 315037-002US
487
Application DMA Unit—Intel
®
81341 and 81342
5.6
Data Alignment
Each channel contains a hardware data alignment unit to support unaligned data
transfers between the source and destination busses. The data alignment unit
optimizes data transfers to and from 32 and 64-bit memory. The channel reformats
data words for the correct bus data width.
Aligned data transfers involve data accesses that fall on natural boundaries. For
example; double words are aligned on 8-byte boundaries and words are aligned on 4-
byte boundaries. ADMA transfers can occur with both the source and destination
addresses unaligned.
5.6.1
64-bit Unaligned Data Transfers
illustrates an ADMA transfer between unaligned 64-bit source and destination
addresses.
Figure 55. Optimization of an Unaligned ADMA Transfer
A6778-01
7
6
5
4
3
2
1
1
15
14
13
12
11
10
9
8
1
1
1
20
19
18
17
16
1
1
1
1
1
1
1
1
Address
Memory
MSB
A000 0200H
A000 0208H
A000 0210H
64-Bit Source Bus
(PCI Bus)
Destination Bus
(Internal Bus)
Programmed Values
Bus Operation
REQ64#
and ACK64#
Sampled
Asserted
1
6
5
4
3
2
1
1
9
8
7
6
5
4
3
2
17
16
15
14
13
12
11
10
1
1
1
1
1
20
19
18
10
4001 0300H
4001 0308H
4001 0310H
4001 0318H
Byte number
double word load @ A0000200
double word load @ A0000208
double word load @ A0000210
0000 0001H
CCR
PADR
0000 0000H
PUADR
BCR
0000 0014H
LADR
0000 0201H
4001 0307H
DCR
0000 0006H
SOURCE
byte store @ 40010307
double word store @ 40010308
double word store @ 40010310
3-byte store @ 40010318
DESTINATION
LSB