LC78620E Datasheet, PDF (29/34 Pages) Sanyo Semicon Device – Compact Disc Player DSP

LC78620E
The DEMO pin can be used when the LC78620E is used in combination with an LA9210M or LA9211M.
By setting this pin high, muting can be set to 0 dB, the disk motor can be set to CLV, and a focus start operation can
be performed, even without issuing any commands from the control microprocessor. Also, since the LASER pin
becomes active, if the mechanism and servo systems are complete, an EFM signal can be acquired with only this
equipment, and an audio signal can be produced without the presence of a microprocessor. However, since the digital
attenuation is set to 100H, this technique is not appropriate for evaluating audio quality.
28. Other Pins; Pin 2:TAI, pin 80: TEST1, pin 12: TEST2, pin 26: TEST3, pin 31: TEST4, pin 74: TEST5, pin 40:
ASDFIR
These pins are used for testing the LSI’s internal circuits. Since the pins TAI and TEST1 to TEST5 have built-in
pull-down resistors, they can be left open in normal operation. ASDFIR must be connected to ground in normal
operation.
29. Circuit Block Operating Descriptions
• RAM address control
The LC78620E 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 LC78620E 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 LC78620E 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.
Position
–4 or less
–3
–2
–1
±0
+1
+2
+3
+4 or more
Division ratio or processing
Force to ±0
589
589
Increase ratio
589
588
Standard ratio
587
587
Decrease ratio
587
Force to ±0
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