92HD71B7 Datasheet, PDF (25/216 Pages) Integrated Device Technology – 4-CHANNEL HD AUDIO CODEC OPTIMIZED FOR LOW POWER

92HD71B7
4-CHANNEL HD AUDIO CODEC OPTIMIZED FOR LOW POWER
PC AUDIO
(the equivalent to a value of 0x0 for the DAC or Volume Knob volume settings) then the
actual gain will be -95.25dB. For example, if the Volume Knob is set to 0x3F (-48dB) and the
DAC amplifier volume is set to 0x1F (-72dB) then the DAC volume will be set to -95.25dB.
• Direct mode is enabled by setting bit 7 in the Volume Knob Cntrl verb (F0F). The volume is
reflected in the Volume Knob Cntrl bits 6:0 and the step size is 0.75dB. In direct mode, soft-
ware can read or write the volume in the Volume Knob widget.
• INDIRECT MODE
• In indirect mode, the Volume Knob widget does not directly control the DAC amplifier gains.
An event on the volume Up/Down pins will increment/decrement the value in the Volume
Knob Cntrl verb (F0F) volume bits (bits 6:0) just as in Direct mode. However, instead of
adjusting the DAC amplifier gain, an unsolicited response is generated (if enabled) and the
control software must read the volume in the Volume Knob widget and take appropriate
action. Indirect mode is particularly useful when it is undesirable to control all of the DAC
amplifier volumes at the same time, or when implementing ADC volume control.
• In indirect mode, there are only 128 volume levels in the Volume Knob Cntrl volume bits, the
value will not go beyond the lower and upper limits (0x0 or 0x7F), and an unsolicited
response will not be generated if an input event tries to go beyond these limits. Therefore, it
is the responsibility of the controlling software to monitor the volume in the Volume Knob
Widget and take appropriate action.
• Indirect mode is enabled by clearing bit 7 in the Volume Knob Cntrl verb (F0F). The volume
is reflected in the Volume Knob Cntrl bits 6:0 and the step size is 0.75dB. In direct mode,
software can read or write the volume in the Volume Knob widget.
1.4.17.3. Hardware Implementation
The Volume Knob interface is comprised of two input pins, CODEC pins 2 and 4. Both pins have
internal pull-up resistors, so only two push button switches are required for most implementations.
Typically, a series resistor and shunt capacitor are used to help reduce noise and prevent damage
from ESD and other potential faults. An example circuit is shown below.
Figure 8. Volume Knob
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4-CHANNEL HD AUDIO CODEC OPTIMIZED FOR LOW POWER
92HD71B7
V 0.9 07/07