Intel 81342 Developer's Manual page 608

7 . 3 . 4 . 1 D D R E C C G e n e r a t i o n
F o r w r i t e o p e r a t i o n s , t h e D M C U g e n e r a t e s t h e e r r o r c o r r e c t i o n c o d e w h i c h i s w r i t t e n
a l o n g w i t h t h e d a t a . T h i s s e c t i o n d e s c r i b e s t h e o p e r a t i o n o f t h e D D R S D R A M C o n t r o l
B l o c k f o r E C C g e n e r a t i o n i n a 6 4 - b i t w i d e m e m o r y a n d 6 4 - b i t r e g i o n . T h e s a m e
p r i n c i p l e s a p p l y f o r 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 , h o w e v e r t h e D M C U 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 T h e a l g o r i t h m f o r a w r i t e t r a n s a c t i o n i s :
if data to write is 64 bits wide
Generate the ECC_with the G-matrix
Write the new data and ECC
else {Partial Write}
Read entire 64-bit data word from memory
Merge the new data portion with the data from memory
Generate the new ECC with the G-matrix
Write new data and ECC
F i g u r e 9 1
t r a n s a c t i o n .
F i g u r e 9 1 . D D R E C C W r i t e F l o w
T h e G - M a t r i x i n
m a t r i x a n d t h e o u t p u t i s t h e E C C c o d e . E a c h r o w o f t h e G - M a t r i x i n d i c a t e s w h i c h d a t a
A D [ 6 3 : 0 ]
b i t s o f
b i t s a r e d r i v e n o n
®
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 0 8
s h o w s h o w t h e d a t a l o g i c a l l y f l o w s t h r o u g h t h e E C C h a r d w a r e f o r a w r i t e
Main
Memory
MCU
Data from Internal Bus
F i g u r e 9 2 g e n e r a t e s t h e E C C . T h e d a t a t o b e w r i t t e n i s i n p u t t o t h e
n e e d s t o b e X O R e d t o g e t h e r t o f o r m t h e E C C b i t . T h e r e s u l t i n g E C C
C B [ 7 : 0 ]
.
®
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
ECC
Memory
Calculate ECC
with G-matrix
A8159-01
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