Intel 81342 Developer's Manual page 686

8 . 3 . 3 . 3 E C C C h e c k i n g
T h e E C C l o g i c u s e s t h e f o l l o w i n g E C C r e a d a l g o r i t h m . T h i s a l g o r i t h m c o r r e c t s t h e d a t a
b e f o r e i t ' s d r i v e n o n t o t h e i n t e r n a l b u s . T h e E C C a l g o r i t h m f o r a r e a d t r a n s a c t i o n i s :
Read 32-bit data and 7-bit ECC
Compute the syndrome by passing the 32-bit data through the G-Matrix and XORing the
7-bit result with the 7-bit ECC
if the syndrome <> 0 {ECC Error}
Look up in H-matrix to determine error type
Register the address where the error occurred
if error is correctable {single bit}
if single-bit error correction is enabled
if single bit error reporting is enabled
else {uncorrectable}
if the read cycle is not part of a RMW cycle {read}
else {write requiring RMW}
if multi-bit error reporting is enabled
W h e n t h e S M C U r e a d s t h e E C C f r o m t h e m e m o r y s u b s y s t e m , i t i s c o m p a r e d ( X O R e d )
w i t h a n E C C r e s u l t t h a t t h e S M C U g e n e r a t e s f r o m t h e d a t a r e a d f r o m t h e m e m o r y . T h e
r e s u l t i n g v a l u e o f t h e X O R o p e r a t i o n i s c a l l e d t h e s y n d r o m e .
S M C U d e c o d e s t h e s y n d r o m e f o r S R A M r e a d c y c l e s .
T a b l e 4 1 6 . S y n d r o m e D e c o d i n g
E r r o r T y p e
N o n e
S i n g l e - B i t
M u l t i - B i t
®
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 8 6
Correct data
Send corrected data to internal bus
Interrupt core for software scrubbing
Target-Abort the Internal Bus read transaction.
Merge the new data portion with the read data from memory
Generate the new ECC with the G-matrix
Write new data and ECC
Interrupt the core for uncorrectable error
T h e s y n d r o m e i s 0 0 0 0 0 0 0 0 .
U s e t h e H - M a t r i x i n F i g u r e 1 0 4
I f t h e S y n d r o m e d o e s n o t m a t c h a n 7 - b i t v a l u e i n t h e H - m a t r i x , t h e e r r o r i s u n c o r r e c t a b l e
®
I n t e l 8 1 3 4 1 a n d 8 1 3 4 2 — S R A M M e m o r y C o n t r o l l e r
S y m p t o m
t o d e t e r m i n e w h i c h b i t t h e S M C U w i l l i n v e r t t o f i x t h e e r r o r .
T a b l e 4 1 6 s h o w s h o w t h e
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