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W h e n t h e m e m o r y t r a n s a c t i o n w r i t e s l e s s t h a n t h e d a t a b u s w i d t h p r o g r a m m e d i n t h e
S D C R , t h e n t h e D D R S D R A M C o n t r o l B l o c k t r a n s l a t e s t h e w r i t e t r a n s a c t i o n i n t o a
r e a d - m o d i f y - w r i t e t r a n s a c t i o n . F o r a p a r t i a l w r i t e , t h e D D R S D R A M C o n t r o l B l o c k c a l c u l a t e s
t h e E C C f o r t h e m o d i f i e d d a t u m a n d w r i t e s i t b a c k . S o , w h e n a n e x t e r n a l u n i t i s s u e s a w r i t e
c y c l e w i t h p a r t i a l d a t a t o a n D M C U p o r t , t h e D M C U :
1 . I s s u e s a 6 4 - b i t ( 3 2 - b i t ) r e a d .
2 . M o d i f i e s t h e v a l u e w i t h t h e n e w p o r t i o n t o b e w r i t t e n .
3 . C a l c u l a t e s t h e E C C o n t h e m o d i f i e d v a l u e .
4 . W r i t e s t h e 6 4 - b i t ( 3 2 - b i t ) v a l u e a n d E C C .
W h e n t h e D M C U d e t e c t s a s i n g l e - b i t e r r o r d u r i n g t h e r e a d , i t i s c o r r e c t e d B E F O R E b e i n g
N o t e :
m e r g e d w i t h t h e w r i t e d a t a s o t h e c o r r e c t e d d a t a i s w r i t t e n b a c k t o t h e a r r a y . W h e n a
m u l t i - b i t e r r o r i s d e t e c t e d , t h e D M C U c a u s e s a n i n t e r r u p t t o t h e c o r e b y w r i t i n g t o t h e
M C I S R . T h e m e m o r y l o c a t i o n i s o v e r w r i t t e n b y t h e D M C U w i t h t h e e r r o r d a t a b u t v a l i d
E C C , m a k i n g t h e c o n t e n t s o f m e m o r y i n v a l i d . F o r m o r e d e t a i l s o n h o w t h e D M C U
h a n d l e s e r r o r c o n d i t i o n s , s e e
p a g e 6 2 1
F i g u r e 9 3
w a v e f o r m i l l u s t r a t e s h o w t h e D D R S D R A M C o n t r o l B l o c k i s s u e s a r e a d - m o d i f y - w r i t e
c y c l e f o r t h e d a t a ( D
I n 3 2 - b i t w i d e m e m o r y a n d i n t h e 3 2 - b i t r e g i o n i n 6 4 - b i t w i d e m e m o r y , t h e D D R
N o t e :
S D R A M C o n t r o l B l o c k s t i l l g e n e r a t e s 8 - b i t w i d e E C C b y z e r o e x t e n d i n g t h e d a t a t o
6 4 - b i t s . A p a r t i a l w r i t e i s a w r i t e o f l e s s t h e n 4 - B y t e s .
F i g u r e 9 3 . S u b 6 4 - b i t D D R S D R A M W r i t e ( D
CK#
CKE
Command
A0-A9,
A11, A12
BA0, BA1
DQS
®
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
6 1 0
S e c t i o n 7 . 5 , " E C C I n t e r r u p t s / E r r o r C o n d i t i o n s " o n
.
s h o w s a n e x a m p l e w h e r e t h e d a t a o f a w r i t e i s l e s s t h a n 6 4 - b i t s w i d e . T h e
) .
1
t
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CK
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ACT
NOP
NOP
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A10
RA
t
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BA x
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DM
®
I n t e l
8 1 3 4 1 a n d 8 1 3 4 2 — D D R S D R A M M e m o r y C o n t r o l l e r
)
0
t
CL
t
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Read
NOP
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COL n
t
t
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CL=2
CAS Latency
Read
ECC Calculation Comparision,
and Correction for D
0
Write
NOP
NOP
NOP
COL n
DIS AP
t DQSS
D out
D in
00
FF
Write
Merge New Data and Generate
New ECC for D
0
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
A7856-02
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