D A T A A L I G N M E N T; B I T U N A L I G N E D D A T A T R A N S F E R S - Intel 81342 Developer's Manual

A p p l i c a t i o n D M A U n i t — I n t e l
5 . 6

D a t a A l i g n m e n t

E a c h c h a n n e l c o n t a i n s a h a r d w a r e d a t a a l i g n m e n t u n i t t o s u p p o r t u n a l i g n e d d a t a
t r a n s f e r s b e t w e e n t h e s o u r c e a n d d e s t i n a t i o n b u s s e s . T h e d a t a a l i g n m e n t u n i t
o p t i m i z e s d a t a t r a n s f e r s t o a n d f r o m 3 2 a n d 6 4 - b i t m e m o r y . T h e c h a n n e l r e f o r m a t s
d a t a w o r d s f o r t h e c o r r e c t b u s d a t a w i d t h .
A l i g n e d d a t a t r a n s f e r s i n v o l v e d a t a a c c e s s e s t h a t f a l l o n n a t u r a l b o u n d a r i e s . F o r
e x a m p l e ; d o u b l e w o r d s a r e a l i g n e d o n 8 - b y t e b o u n d a r i e s a n d w o r d s a r e a l i g n e d o n 4 -
b y t e b o u n d a r i e s . A D M A t r a n s f e r s c a n o c c u r w i t h b o t h t h e s o u r c e a n d d e s t i n a t i o n
a d d r e s s e s u n a l i g n e d .
5 . 6 . 1

6 4 - b i t U n a l i g n e d D a t a T r a n s f e r s

F i g u r e 5 5
a d d r e s s e s .
F i g u r e 5 5 . O p t i m i z a t i o n o f a n U n a l i g n e d A D M A T r a n s f e r
D e c e m b e r 2 0 0 7
O r d e r N u m b e r : 3 1 5 0 3 7 - 0 0 2 U S
®
8 1 3 4 1 a n d 8 1 3 4 2
i l l u s t r a t e s a n A D M A t r a n s f e r b e t w e e n u n a l i g n e d 6 4 - b i t s o u r c e a n d d e s t i n a t i o n
MSB
64-Bit Source Bus
(PCI Bus)
REQ64#
and ACK64#
Sampled
Asserted
Destination Bus
(Internal Bus)
Programmed Values
CCR 0000 0001H
PADR
0000 0201H
PUADR
0000 0000H
LADR
4001 0307H
BCR
0000 0014H
DCR 0000 0006H
Memory
7 6 5 4 3
15 14 13 12 11
1 1 1 20 19
1 1 1 1 1
1 6 5 4 3
9 8 7 6 5
17 16 15 14 13
1 1 1 1 1
Bus Operation
SOURCE
double word load @ A0000200 byte store @ 40010307
double word load @ A0000208 double word store @ 40010308
double word load @ A0000210 double word store @ 40010310
3-byte store @ 40010318
LSB
Address
2 1 1
A000 0200H
10 9 8
A000 0208H
18 17 16
A000 0210H
1 1 1
2 1 1
4001 0300H
4 3 2
4001 0308H
12 11 10
4001 0310H
20 19 18
4001 0318H
10
Byte number
DESTINATION
A6778-01
®
I n t e l 8 1 3 4 1 a n d 8 1 3 4 2 I / O P r o c e s s o r s
D e v e l o p e r ' s M a n u a l
4 8 7