92hd71b5x5prgxb3x8 Integrated Device Technology, 92hd71b5x5prgxb3x8 Datasheet - Page 22

• Manufacturer Part Number: 92hd71b5x5prgxb3x8
• Description: Four Channel Hd Audio Codec, Low Power Optimized, 4-ports, 95db Snr
• Manufacturer: Integrated Device Technology

4-CHANNEL HD AUDIO CODECS OPTIMIZED FOR LOW POWER
92HD71B5
4-CHANNEL HD AUDIO CODECS OPTIMIZED FOR LOW POWER
1.4.16. External Volume Control
1.4.15.3. VRefOut/GPIO Selection
Two functions are available on pin 31. To determine which function is actually enabled, the order of
precedence is followed:
1) If the GPIO4 function is enabled, it overrides VRefOut-E
2) If the GPIO4 function is not enabled through the AFG, then, at reset the VrefOut-E is enabled.
3) If using pin 31 as GPIO, make sure to incorporate a 10K ohm external pull-up to AVDD to prevent
the pin from floating in GPI mode and to allow proper operation in open-drain GPO mode.
92HD71B5 incorporates a 2-pin volume control interface. Volume up, down, and mute functions are
easily implemented using 2 push-button switches. The CODEC provides internal pull-up resistors
simplifying external CODEC circuitry. Also, repeat and direct modes of operation add flexibility to the
interface. The typical usage model is for front panel master volume buttons on an entertainment PC,
or case mounted hardware volume control for mobile platforms.
1.4.16.1. Theory of Operation
The codec monitors the volume up/down inputs for a change of state from high to low, and waits for
the inputs to settle. If the inputs have not settled by the end of the de-bounce period, then the value
at the end of the period is used. A 0 (low voltage) on the Down pin will decrement the volume regis-
ter, while a 0 on the Up pin will increment the volume register. If both inputs are 0 at the same time,
then the volume register will be set to its lowest value (mute). Pressing Up, Down, or both buttons at
the same time when the volume control interface is in mute mode, will cause the part to un-mute.
The de-bounce / repeat rate is selectable from 2.5Hz to 20Hz in 2.5Hz increments using the Volume
Knob VCSR0 verb (FE0) Rate bits (bits 2:0). This value is used for both de-bounce and repeat rates.
The de-bounce period is the time that the CODEC waits for the inputs to settle, and the repeat rate is
the rate at which the CODEC will increment/decrement the volume if a volume button is pushed and
held. When a falling edge is detected on either one of the volume control pins, the codec will wait for
(1/Rate) seconds for the input to settle. If the Continuous bit is set in the Volume Knob VCSR0 verb
(bit 3), then the codec will wait for the de-bounce period to expire then repeatedly increment or dec-
rement the volume register at the rate specified in the Rate bits until the button is released.
1.4.16.2. Modes of Operation
•
DIRECT MODE
•
In Direct mode, the Volume Knob widget directly controls the volume of all of the DACs in
the part. The volume in the Volume Knob widget acts as the master volume and limits the
maximum volume for each of the DAC amplifiers. The amp gain for each of the DACs can
also be adjusted using the DAC amplifiers. However, the actual gain for an individual DAC
will be the sum of the Volume Knob volume and the DAC amplifier volume. For example, if
the DAC amplifier gain is set to 0x7F (0dB) and the Volume Knob volume is set to 0x3F
(-48dB) the resulting gain would be -48dB. If the combination of gains is less than -95.25dB
(the equivalent to a value of 0x0 for the DAC or Volume Knob volume settings) then the
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92HD71B5
PC AUDIO
V 1.0, 01/08