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M64403FP

ERROR CORRECTION WITH VARIABLE LENGTH AND DISTANCE

MITSUBISHI ELECTRIC  

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MITSUBISHI ICs (LSI)

M64403FP

ERROR CORRECTION WITH VARIABLE LENGTH AND DISTANCE

CORRECTED DATA OUTPUT METHOD

When the decode operation finishes and correction result is able to

output to a code word, OUTR changes to H for one period for

CLKO. In this case, error location data is shown on ELO0 to ELO7,

error value is shown on DAO0 to DAO7 and error correction count

or erasure count is shown on ENM0 to ENM7. (Details are

described later.)

When output enable signals (LOEN, DOEN, NOEN) are set to L

(active mode), respective data (error location, error value, error or

erasure count) are able to output. When these output enable

signals are set to H, respective data bus change to high

impedance status.

Error location data (ELO0 to ELO7) 00 hex means the location of

head data for input code word.

Error value data (DAO0 to DAO7) corresponds with error location

data (ELO0 to ELO7).

ADDC should be L for one period of CLKO in order to output next

error location and next error value.

(See page10 : Correction data operation sequence chart)

ENM0 to ENM4 outputs error correcting count at ERMF=L, erasure

count at ERMF=H. This erasure count means real error count at

constrained error correction mode, total count for real error and

erasure at erasure correction priority mode. And this erasure count

includes empty erasure (it means error value is zero). If erasure

count excesses 31 dec, ENM0 to ENM4 shows 31 dec.

After the external circuit read error count/error location/error value

for a code word, OTRG should change L to H only one time by

synchronization with CLKO clock. Data shift for internal pipe line

circuit is executed by this operation. If this operation is so late,

registers in the internal pipe line become full. And data collision

may occur if code word is input more and its syndrome data is

generated. In this case, M64403FP informs external of its status

and SYCR changes to H. (If the last symbol of code word is input

at SBFB=H, decoding is operated safely.)

SYCR which changes to H is reset by system reset (REST=L).

OUTPUT CONTROL SIGNAL

When OUTR changes to H, CORF (error detected flag), UNCF

(uncorrectable flag) and EROV (erasure over flag) are output.

CORF changes to L when M64403FP regards input code word as

no error. CORF changes to H when M64403FP detects error.

UNCF changes to H when M64403FP regards the error correction

as impossible. If the input erasure flag count excesses erasure

threshold value with erasure correction priority mode, UNCF

changes to H also.

OMD0 to OMD2 show the current operated code word's decode

mode which was set by MOD0 to MOD2.

INTERNALCORRECTION MODE

The internal correction mode is active when the bit3 (D3) of

parameter register address-E is set to H. In this internal correction

mode, the code word that was input already and shown by OMD0

to OMD2 input to ELO0 to ELO7.

In order to recognize the header symbol of input data, OTRG

should be H by synchronization with the header symbol of code

word. ADDC should be L while valid code word is input.

Corrected data is output from DAO0 to DAO7 after three clocks

delay. OUTR changes to H by synchronization with header symbol

in order to show the header symbol of corrected code word. CRDY

changes to L by synchronization with output code word. CRDF

changes to H for corrected portion. In addition, ORDY changes to

H while output period of information symbol in order to distinguish

from code word from information symbol and check symbol.

MISOPERATION FOR ODD CHECK BYTE

NUMBER

M64403FP have no good operation when check byte number are

just d/2 (d=check byte number+1) as UNCF don't to change to H,

and misdata is output.

But we can judge the misoperation when ENM<4:0> indicates d/2

in error correction mode, and ENM<4:0> indicates d/2 when

erasure number=0 or EROV=H in erasure correction mode.

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