74F632QC NSC [National Semiconductor], 74F632QC Datasheet - Page 7

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

Memory
Read
Read
Read
Modify
Write
Read
Latch Input Check
Word while Data
Input Latch
Remains
Transparent
Latch Diagnostic
Data Word into
Output Latch
Latch Diagnostic
Data Word into
Input Latch
Output Diagnostic
Data Word
Syndrome Bits
Output Corrected
Diagnostic Data
Word
Syndrome Bits
Cycle
Functional Description
two bit locations
OEB
Diagnostic data is a data word with an error in one bit location except when testing the MERR error flag In this case the diagnostic data word will contain errors in
Function
0
EDAC
controls DB
Flag
Output
Read
Latch Input
Data
Check Bits
Latch Corrected
Data Word into
Output Latch
Modify
Appropriate
Byte or Bytes
Check Word
Generate New
Function
EDAC
0
–DB
Flag
7
(BYTE
S
H
H
H
H
L
L
1
Control
0
) OEB
S
H
H
H
H
H
L
S
H
H
H
L
0
1
Control
1
controls DB
Input Correct
Data Word
Input
Diagnostic
Data Word
Input
Diagnostic
Data Word
Latched
Input
Diagnostic
Data Word
Output
Diagnostic
Data Word
Output
Corrected
Diagnostic
Data Word
(Continued)
S
Data I O
H
H
L
L
0
TABLE VI Read-Modify-Write Function
8
–DB
TABLE VII Diagnostic Function
Input
Latched
Input
Data
Latched
Output
Data
Word
Input
Modified
BYTE
Output
Unchanged
BYTE
15
BYTEn
(BYTE
0
0
1
DB Byte
Control
) OEB
OEB
H
H
H
H
L
L
n
OEBn
2
controls DB
7
H
H
H
H
L
DB Output
LEDBO
Latch
DB Output
16
H
H
H
X
L
L
LEDBO
–DB
Latch
H
H
X
L
23
(BYTE
Input Correct
Check Bits
Latched
Input
Check Bits
Output
Latched
Check Bits
High Z
Output
Syndrome
Bits
High Z
Output
Syndrome
Bits
High Z
Output
Syndrome
Bits
High Z
Check I O
2
) OEB
Input
Latched
Input
Check Word
High Z
Output
Syndrome
Bits
Output
Check Word
Check I O
3
controls DB
Control
OECB
Control
24
OECB
CB
H
H
H
H
H
H
L
L
L
L
CB
–DB
H
H
H
L
L
31
(BYTE
Enabled
Enabled
Enabled
ERR
ERR
Error Flags
Error Flags
H
3
)
Enabled
Enabled
Enabled
Enabled
Enabled
H
MERR
MERR
H