LC78620E Datasheet, PDF (23/34 Pages) Sanyo Semicon Device – Compact Disc Player DSP

LC78620E
• Attenuation setup
Since the attenuation level is set to the muted state (a muting of –∞ is specified by an attenuation coefficient of
00H) after the attenuation level is reset, the attenuation coefficient must be directly set to EEH (using the ATT
DATA SET command) to output audio signals. Note that the attenuation level can be set to one of 239 values from
00H to EEH. These two-byte commands differ from the two-byte commands used for track counting in that it is
only necessary to set RWC once and a two-byte command reset is not required. (See the item on two-byte
commands (RWC set once) on page 10.)
After inputting the target attenuation level as a value in the range 00H to EEH, sending an attenuator step up/down
command will cause the attenuation level to approach the target value in steps of 4, 8, or 16 units as specified in
synchronization with rising edges on the LRSY input. However, the ATT DATA SET command sets the target
value directly. If a new data value is input during the transition, the value begins to approach the new target value
at that point. Note that the UP/DOWN distinction is significant here.
ATT DATA
Audio output level = 20 log _100H [dB]
For example, the formula below calculates the time required for the attenuation level to increase from 00H to EEH
when a 4STEP UP command is executed. Note that the control microprocessor must provide enough of a time
margin for this operation to complete before issuing the next attenuation level set command.
238 level × 4STEP UP
44.1 kHz (LRSY) ^{≈ 21.6 ms}
Note: Setting the attenuation level to values of EFH or higher is disallowed to prevent overflows in one-bit D/A
converter calculations from causing noise.
• Mute output; Pin 46: MUTEL, pin 55: MUTER
These pins output a high level when the attenuator coefficient is set to 00H and the data in each channel has been
zero for a certain period. If data input occurs once again, these pins go low immediately.
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