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參數資料
| 型號： | LC78625E |
| 元件分類： | 消費家電 |
| 英文描述： | SPECIALTY CONSUMER CIRCUIT, PQFP80 |
| 封裝： | QFP-80 |
| 文件頁數： | 24/35頁 |
| 文件大?。?/td> | 535K |
| 代理商： | LC78625E |
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No. 5502-30/35
LC78625E
29. Other pins; Pin 2:TAI, pin 80: TEST1, pin 12: TEST2, pin 26: TEST3, pin 31: TEST4, pin 74: TEST5
These pins are used for testing the LSI's internal circuits. Although the pins TAI and TEST1 to TEST5 have built-in
pull-down resistors, they should be connected to ground (0 V) for safety.
30. Circuit Block Operating Descriptions
RAM address control
The LC78625E incorporates an 8-bit
× 2k-word RAM on chip. This RAM has an EFM demodulated data jitter
handling capacity of ±4 frames implemented using address control. The LC78625E continuously checks the remaining
buffer capacity and controls the data write address to fall in the center of the buffer capacity by making fine
adjustments to the frequency divisor in the PCK side of the CLV servo circuit. If the ±4 frame buffer capacity is
exceeded, the LC78625E forcibly sets the write address to the ±0 position. However, since the errors that occur due to
this operation cannot be handled with error flag processing, the IC applies muting to the output for a 128 frame period.
C1 and C2 error correction
The LC78625E writes EFM demodulated data to internal RAM to compensate for jitter and then performs the
following processing with uniform timing based on the crystal oscillator clock. First, the LC78625E performs C1 error
checking and correction in the C1 block, determines the C1 flags, and writes the C1 flag register. Next, the LC78625E
performs C2 error checking and correction in the C2 block, determines the C2 flags, and writes data to internal RAM.
Note: 1. If the positions of the errors determined by the C2 check agree with the those specified by the C1 flags, the correction is performed and the flags
are cleared. However, if the number of C1 flags is 7 or higher, C2 correction may fail. In this case correction is not performed and the C1 flags are
taken as the C2 flags without change. Error correction is not possible if one error position agrees and the other does not. Furthermore, if the
number of C1 flags is 5 or under, the C1 check result can be seen as unreliable. Accordingly, the flags will be set in this case. Cases where the
number of C1 flags is 6 or more are handled in the same way, and the C1 flags are taken as the C2 flags without change. When there is not even
one agreement between the error positions, error correction is, of course, impossible. Here, if the number of C1 flags was 2 or under, data that
was seen as correct after C1 correction is now seen as incorrect data. The flags are set in this case. In other cases, the C1 flags are taken as the
C2 flags without change.
2. When data is determined to have three or more errors and be uncorrectable, correction is, of course, impossible. Here, if the number of C1 flags
was 2 or under, data that was seen as correct after C1 correction is now seen as incorrect data. The flags are set in this case. In other cases the
C1 flags are taken as the C2 flags without change.
Position
Divisor or Handling
–4 or lower
Forcibly moves to ±0
–3
589
–2
589
Advancing divisors
–1
589
±0
588
Standard divisor
+1
587
+2
587
Decreasing divisors
+3
587
+4 or greater
Forcibly moves to ±0
C1 Check
Correction and Flag Processing
No errors
Correction not required flags cleared
Single error
Correction performed flags cleared
Dual errors
Correction performed flags set
Three or more errors
Correction not possible flags set
C2 Check
Correction and Flag Processing
No errors
Correction not required flags cleared
Single error
Correction performed flags cleared
Dual errors
C1 flags referenced. Note 1
Three or more errors
C1 flags referenced. Note 2
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