74F632QC NSC [National Semiconductor], 74F632QC Datasheet - Page 5

• Manufacturer Part Number: 74F632QC
• Description: 32-Bit Parallel Error Detection and Correction Circuit
• Manufacturer: NSC [National Semiconductor]

Memory
Read
Read
Read
Cycle
Functional Description
Note 1 See Table III for error description
Note 2 See Table V for error location
6
L
L
L
L
L
L
L
L
L
L
L
L
L
L
L
L
L
L
L
L
L
L
L
L
L
L
L
L
L
L
L
L
5
L
L
L
L
L
L
L
L
L
L
L
L
L
L
L
L
L
L
L
L
L
L
L
L
L
L
L
L
L
L
L
L
Latch Input
Data
Bits
Output
Corrected Data
Read
Syndrome Bits
Function
Syndrome Bits
EDAC
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
4
L
L
L
L
L
L
L
L
L
L
L
L
L
L
L
L
Check
Flag
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
3
L
L
L
L
L
L
L
L
L
L
L
L
L
L
L
L
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
2
L
L
L
L
L
L
L
L
L
L
L
L
L
L
L
L
S
H
H
H
Control
1
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
1
L
L
L
L
L
L
L
L
L
L
L
L
L
L
L
L
S
H
H
L
(Continued)
0
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
0
L
L
L
L
L
L
L
L
L
L
L
L
L
L
L
L
TABLE IV Read Flag and Correct Function
Input
Latched
Input
Data
Output
Corrected
Data Word
Data I O
2-Bit (Note 2)
TABLE V Syndrome Decoding
Error
DB
DB
DB
DB
DB
DB
DB
DB
2-Bit
2-Bit
2-Bit
2-Bit
2-Bit
2-Bit
2-Bit
2-Bit
2-Bit
2-Bit
2-Bit
2-Bit
2-Bit
2-Bit
2-Bit
unc
unc
unc
unc
unc
unc
unc
unc
31
30
29
28
27
26
25
24
DB Control
OEB
H
H
L
5
n
CB
DB
2-Bit
unc
Note 2-bit and unc condition will cause both ERR and MERR to be LOW
Note 1 Syndrome bits for all LOWs MERR and ERR LOW for all LOWs
only ERR LOW for DB
Note 2 Syndrome bits for all HIGHs
X
Y
6
L
L
L
L
L
L
L
L
L
L
L
L
L
L
L
L
L
L
L
L
L
L
L
L
L
L
L
L
L
L
L
L
e
e
e
e
DB Output
Uncorrectable multi-bit error
LEDBO
Error in check bit X
Error in data bit Y
Double-bit error
Latch
X
X
L
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
5
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
Syndrome Bits
4
L
L
L
L
L
L
L
L
L
L
L
L
L
L
L
L
30
Input
Latched
Input
Check Word
Output
Syndrome
Bits (Note 2)
Check I O
error
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
3
L
L
L
L
L
L
L
L
L
L
L
L
L
L
L
L
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
2
L
L
L
L
L
L
L
L
L
L
L
L
L
L
L
L
Control
OECB
CB
H
H
L
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
1
L
L
L
L
L
L
L
L
L
L
L
L
L
L
L
L
Enabled (Note 1)
Enabled (Note 1)
Enabled (Note 1)
ERR
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
0
L
L
L
L
L
L
L
L
L
L
L
L
L
L
L
L
Error Flags
Error
2-Bit
2-Bit
2-Bit
2-Bit
2-Bit
2-Bit
2-Bit
2-Bit
2-Bit
2-Bit
2-Bit
2-Bit
2-Bit
2-Bit
2-bit
2-bit
DB
DB
DB
DB
DB
DB
DB
DB
CB
unc
unc
unc
unc
unc
unc
unc
MERR
7
6
5
4
3
2
0
1
6