TABLE VI Read-Modify-Write Function

Memory

EDAC

Control

DB Output

CB

Error Flags

Cycle

Function

BYTEn

OEBn

Latch

Check IO

Control

ERR

MERR

LEDBO

OECB

Read

Read

Flag

H

L

Input

H

X

Input

H

Enabled

Read

Latch Input

Latched

Latched

Data

H

H

Input

H

L

Input

H

Enabled

Check Bits

Data

Check Word

Read

Latch Corrected

Latched

High Z

H

Data Word into

HH

Output

HH

Output

L

Enabled

Output Latch

Data

Syndrome

Word

Bits

Modify

Modify

Input

Write

Appropriate

Modified

H

Byte or Bytes

LL

H

Output

LH

H

Generate New

Output

Check Word

Check Word

Unchanged

L

TABLE VII Diagnostic Function

EDAC

Control

DB Byte

DB Output

CB

Error Flags

Function

Data IO

Control

Latch

Check IO

Control

ERR

MERR

LEDBO

OECB

Read

Flag

HL

Input Correct

HX

Input Correct

HH

Data Word

Check Bits

Latch Input Check

Word while Data

Input

Latched

Input Latch

L

H

Diagnostic

H

L

Input

H

Enabled

Remains

Data Word

Check Bits

Transparent

Latch Diagnostic

Input

Output

Data Word into

L

H

Diagnostic

H

H

Latched

L

Output Latch

Data Word

Check Bits

Enabled

High Z

H

Latch Diagnostic

Latched

Output

Data Word into

HH

Input

HH

Syndrome

L

Enabled

Input Latch

Diagnostic

Bits

Data Word

High Z

H

Output Diagnostic

Output

Output

Data Word

H

H

Diagnostic

L

H

Syndrome

L

Enabled

Syndrome Bits

Data Word

Bits

High Z

H

Output Corrected

Output

Output

Diagnostic Data

HH

Corrected

LL

Syndrome

L

Enabled

Word

Output

Diagnostic

Bits

Syndrome Bits

Data Word

High Z

H

Diagnostic data is a data word with an error in one bit location except when testing the MERR error flag In this casethe diagnostic data word will contain errors in

two bit locations

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