![](http://datasheet.mmic.net.cn/50000/92HD88B1X5NDGXYYX8_datasheet_1923415/92HD88B1X5NDGXYYX8_32.png)
IDT CONFIDENTIAL
32
V 0.995 01/11
2009 INTEGRATED DEVICE TECHNOLOGY, INC.
92HD88
SINGLE CHIP PC AUDIO SYSTEM, CODEC+MONO SPEAKER AMPLIFIER+CAPLESS HP+LDO
The filter is implemented in digital before the Digital to Analog converter. There are 2 major conse-
quences to implementing the filter in the digital domain:
1. All ports connected to the DAC will be affected by the high-pass filer when it is enabled.
2. Analog paths (such as when the microphone input is routed through the mixer to the BTL ampli-
fier) are not affected.
Like the other analog inputs, PC_Beep is not affected by the digital high-pass filter. To ensure that
the speakers attached to the BTL amplifier are not harmed by low frequency audio entering the
PC_Beep input, an external filter must be implemented. Fortunately, it is common practice to imple-
ment an attenuation circuit and DC blocking capacitor at the PC_Beep input. This attenuator/filter is
easily adjusted to restrict low frequency audio. The easiest approach is to reduce the value of the
DC blocking capacitor but other approaches are equally effective.
2.20. GPIO
2.20.1. GPIO Pin mapping and shared functions
2.20.2. SPDIF/Digital Microphone/GPIO Selection
3 functions are available on the DMIC_1/GPIO0/SPDIFOUT1 pin (pin 38). To determine which func-
tion is enabled, the order of precedence is followed:
3. If the GPIOs are enabled, they override both SPDIF_OUT and Digital Mics
4. If the GPIOs are not enabled through the AFG, then at reset, the pin is pulled low by an internal
pull-down resistor.
5. If the port is enabled as an input, the digital microphones will be used.
6. If the port is enabled as an output, the SPDIF output will be used.
7. In the event that the port is enabled as an input and an output, the port will be an output and the
Digital Mic path will be mute.
2.20.3. Digital Microphone/GPIO Selection
2 functions are available on the DMIC_CLK/GPIO1 (pin 2) and the DMIC_0/GPIO2 (pin 3) pins. To
determine which function is enabled, the order of precedence is followed:
1. If GPIOs are not enabled through the AFG, then at reset, pins 2 and 4 are pulled low by an inter-
nal pull-down resistor.
2. If the GPIO 1 is enabled, the 2 DMIC pins become mute (unless programmed for GPIO or SPDIF
use) and pin 2 becomes an internal pull-down.
3. If GPIO2 is enabled through the AFG, pin 3 becomes a GPIO and is pulled low by an internal
pull-down resistor.
4. If the port is enabled as an input, the digital microphones will be used.
5. If the port is not enabled as an input or if the pin is configured as a GPIO, the digital microphone
path will be mute.
GPIO
#
Pin
Supply SPDIF
In
SPDIF
Out
GPI/O
GPI
GP
O
VrefOut
DMIC
VOL
Pull
Up
Pull
Down
0
38
DVDD
YES
IN
50K
1
2
DVDD
YES
CLK
50K
2
3
DVDD
YES
IN
50K