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DP8402A Datasheet(PDF) 5 Page - National Semiconductor (TI)

[Old version datasheet] Texas Instruments acquired National semiconductor.
Part No. DP8402A
Description  DP8402A/DP8403/DP8404/DP8405 32-Bit Parallel Error Detection and Correction Circuits (EDACs)
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Manufacturer  NSC [National Semiconductor (TI)]
Direct Link  http://www.national.com
Logo NSC - National Semiconductor (TI)

DP8402A Datasheet(HTML) 5 Page - National Semiconductor (TI)

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Memory Read Cycle (Error Detection
Correction Details) (Continued)
1) Single data bit errors cause 3 or 5 bits in the syndrome
word to go low The columns of the check bit syndrome
matrix (TABLE II) are the syndrome words for all single bit
data errors in the 32 bit word (also see TABLE V) The
data bit in error corresponds to the column in the check
bit syndrome matrix that matches the syndrome word
For instance the syndrome word indicating that data bit
31 is in error would be (CB6-CB0) e ‘‘0001010’’ see the
column for data bit 31 in TABLE II or see TABLE V
During mode 3 (S0 e S1 e 1) the syndrome word is
decoded during single data bit errors and used to invert
the bit in error thus correcting the data word The correct-
ed word is made available on the data IO port (DB0 thru
DB31) the check word IO port (CB0 thru CB6) presents
the 7-bit syndrome error code This syndrome error code
can be used to locate the bad memory chip
2) A single check bit error will cause that particular check bit
to go low in the syndrome word
3) A double bit error will cause an even number of bits in the
syndrome word to go low The syndrome word will then
be the EXCLUSIVE NOR of the two individual syndrome
words corresponding to the 2 bits in error The two-bit
error is not correctable since the parity tree can only
identify single bit errors
If any of the bits in the syndrome word are low the ‘‘ERR’’
flag goes low The ‘‘MERR’’ (dual error) flag goes low during
any double bit error conditions (See Table III)
Three or more simultaneous bit errors can cause the EDAC
to believe that no error a correctable error or an uncorrect-
able error has occurred and will produce erroneous results
in all three cases It should be noted that the gross-error
conditions of all lows and all highs will be detected
TABLE V Syndrome Decoding
Syndrome Bits
Error
6 5 43210
L L LLLLL
unc
L L LLLL H
2-bit
L L L L L H L
2-bit
LL L L L HH
unc
L L L L H L L
2-bit
L L L LHLH
unc
LL L L HH L
unc
L L L L H H H
2-bit
L L L H L L L
2-bit
L LLHL LH
unc
L LLHLHL DB31
L LLHLH H
2-bit
L LLH HL L
unc
L L L H H L H
2-bit
L L L H H H L
2-bit
LL L HHHH DB30
L L H LLLL
2-bit
LLH L L L H
unc
L L H L L H L DB29
L L H L L H H
2-bit
L L HLHL L DB28
L L HLHLH
2-bit
L L H L H H L
2-bit
L L H L H H H DB27
LLHH L L L DB26
LLHH L L H
2-bit
L L H HLHL
2-bit
L L H H L H H DB25
LLHHH L L
2-bit
LLHHH L H DB24
LLHHHH L
unc
LLHHHHH
2-bit
CB X e error in check bit X
DB Y e error in data bit Y
2-bit e double-bit error
unc e uncorrectable multibit error
Syndrome Bits
Error
6 543210
L H L L L L L
2-bit
L H LLLL H
unc
L H L L LHL
DB7
L H L L L H H
2-bit
L H L L H L L
DB6
L H L L H L H
2-bit
L H L L H H L
2-bit
LH L L HHH
DB5
L HLHL L L
DB4
L H L H L L H
2-bit
L H L H L H L
2-bit
L HLHLH H
DB3
L H L H H L L
2-bit
L HLH HLH
DB2
L HLH H H L
unc
L H L H H H H
2-bit
LHH L L L L
DB0
L H H L L L H
2-bit
L H H L L H L
2-bit
LHH L L HH
unc
L H H L H L L
2-bit
LHH L H L H
DB1
LHH L H H L
unc
L H H L H H H
2-bit
LHHH L L L
2-bit
LHHH L L H
unc
LHHH L H L
unc
LHHH L H H
2-bit
LHHHH L L
unc
LHHHH L H
2-bit
LHHHHH L
2-bit
LHHHHHH
CB6
Syndrome Bits
Error
654 3 2 1 0
H L L L L L L
2-bit
H L LLLL H
unc
H L L L LHL
unc
H L L L L H H
2-bit
H L L L H L L
unc
H L L L H L H
2-bit
H L L L H H L
2-bit
HL L L HHH
unc
H LLHL L L
unc
H L L H L L H
2-bit
H L L H L H L
2-bit
H L L H L H H DB15
H L L H H L L
2-bit
H LLH HLH
unc
H L L H H H L DB14
H L L H H H H
2-bit
HLH L L L L
unc
H L H L L L H
2-bit
H L H L L H L
2-bit
H L H L L H H DB13
H L H L H L L
2-bit
H L H L H L H DB12
H L H L H H L DB11
H L H L H H H
2-bit
HLHH L L L
2-bit
HLHH L L H DB10
HLHH L H L
DB9
HLHH L H H
2-bit
HLHHH L L
DB8
HLHHH L H
2-bit
HLHHHH L
2-bit
HLHHHHH
CB5
Syndrome Bits
Error
6543210
H H LLLLL
unc
H H LLLL H
2-bit
H H L L L H L
2-bit
H H L L L H H DB23
H H L L H L L
2-bit
H H L LHLH DB22
H H L L H H L DB21
H H L L H H H
2-bit
H H L H L L L
2-bit
H HLHL LH DB20
H HLHLHL DB19
H HLHLH H
2-bit
H H L H H L L DB18
H H L H H L H
2-bit
H H L H H H L
2-bit
HH L HHHH
CB4
H H H LLLL
2-bit
H H H L L L H DB16
HHH L L H L
unc
H H H L L H H
2-bit
H H HLHL L DB17
H H HLHLH
2-bit
H H H L H H L
2-bit
HHH L HHH
CB3
HHHH L L L
unc
HHHH L L H
2-bit
H H H HLHL
2-bit
HHHH L H H
CB2
HHHHH L L
2-bit
HHHHH L H
CB1
HHHHHH L
CB0
HHHHHHH none
5


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