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CM 108AH Highly Integrated USB Audio I/O Controller www .cmedia.com.tw Copyright© C-Media Electro nics Inc. R ev . 2.1 ︱ P age 15/27 7.2 Ju mper Pins and Mode Setting: The CM108AH can be configured via several jumpe r pi…
CM108AH
Highly Integrated USB Audio I/O Controller
www.cmedia.com.tw
Copyright© C-Media Electronics Inc. Rev. 2.1︱ Page 14/27
7.1.4 USB Audio Topology Diagram
IT
IT
OT
OT
USB Out
Microphone In
Feature Unit
(volume) (mute)
Speakerout
USBIN
Feature Unit
(volume) (mute)
ID = 01
ID=02
ID= 0A
ID = 09
ID = 06
ID = 07
Feature Unit
(volume) (mute)
ID = 0D
Mixer Unit
ID = 0F
selector Unit
ID = 08
enable or disable by
MSEL pin
CM108AH
Highly Integrated USB Audio I/O Controller
www.cmedia.com.tw
Copyright© C-Media Electronics Inc. Rev. 2.1︱ Page 15/27
7.2 Jumper Pins and Mode Setting:
The CM108AH can be configured via several jumper pins. These jumper pin settings affect both USB descriptors
and USB audio topology.
7.2.1 MODE Pin and MSEL Pin
If the MODE pin is pushed up to 3.3V (speaker mode), a playback-only function is activated and no recording
function is declared to the host. At this setting, t h e MSEL pin is ignored and only one input terminal, one
output terminal and one feature unit is declared in the USB audio topology.
If the MODE pin is pulled low (headset mode), a full-duplex playback and recording function is reported to the
host. The MSEL pin setting activates one mixer unit and one feature unit.
When MSEL = 1, the mixer is enabled (AA-path enabled), but with default mute setting
When MSEL = 0, the mixer is disabled (AA-path disabled)
The above USB audio topology (7.1.4) is an example of headset mode with enabled mixer.
7.2.2 MODE Pin and PWRSEL Pin
The PWRSEL pin affects the power configuration of the CM108AH. Together with the MODE pin, there are a
total of 4 programmable combinations.
Combinations
MODE
3.3V
GND
PWRSEL
3.3V
Speaker mode:
Playback only
(100mA self-powered)
Headset mode:
Playback and recording
(100mA Bus-powered)
GND
Speaker mode:
Playback only
(500mA Bus-powered)
Headset mode:
Playback and recording
(500mA Bus-powered)
USB Audio Topology Diagram
CM108AH
Highly Integrated USB Audio I/O Controller
www.cmedia.com.tw
Copyright© C-Media Electronics Inc. Rev. 2.1︱ Page 16/27
7.3 HID Feature
The CM108AH’s HID feature allows users to set volume up, volume down, playback mute and recording mute
button pins, and reports the changes to the host to synchronize host side settings. In addition, all CM108AH
internal registers can be accessed via HID function call.
7.3.1 What’s HID?
USB protocols can configure devices at startup or when they are plugged in at run time. These devices are
categorized into various device classes. Each device class defines the common behavior and protocols for
devices that serve similar functions. The HID (Human Interface Device) class is one of the device classes.
The HID class consists primarily of devices that are used to control the operation of computer systems.
Typical examples of HID class devices include:
Keyboards and pointing devices: mice, trackballs and joysticks
Front-panel controls: knobs, switches, buttons and sliders
Controls that might be found on VCR remote controls, games or simulation devices: data gloves,
throttles, and steering wheels
Devices that may not require human interaction but provide data in a similar format to HID class
devices: bar-code readers, thermometers or voltmeters