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CM108B USB Audio Single C hip Datasheet Revision: 1.11 www .cmedia.com.tw P age 12 / 24 Copyright© C -Media Electr onics Inc. Offset Field Size Value (Hex) Description 0 bLength 1 09 T otal 9 Bytes 1 bDescriptorType 1 02…
CM108B
USB Audio Single Chip
Datasheet Revision: 1.11 www.cmedia.com.tw
Page 11 / 24 Copyright© C-Media Electronics Inc.
7 Function description
7.1 USB interface
The CM108B integrates USB transceiver, PLL and regulator modules, meaning only a few passive components are
necessary for USB interface connection. Default USB descriptors are embedded in the CM108B, so no additional
design effort is needed for generic USB operation. For custom orders, customers can attach a 93C46 EEPROM to
override the embedded VID, PID, product and manufacturer strings, and initial/max/min volume settings. The
CM108B automatically detects the 93C46, and the overwrite function is performed at start up.
7.1.1 USB audio topology diagram for headset
The CM108B supports headset and speaker topology that can be selected by MODE pin. The topology setting as
following: MODE=0, Headset Topology; MODE=1, Speaker Topology
0X01
IT
0X0F
MIXER
0X09
FEA
0X06
OT
0X02
IT
0X0A
FEA
0X08
SEL
0X07
OT
0X0D
FEA
Device Descriptor
Offset
Field
Size
Value (Hex)
Description
0
bLength
1
12
Total 18 Bytes
1
bDescriptorType
1
01
Device Descriptor
2
bcdUSB
2
0110
USB 1.1 compliant.
4
bDeviceClass
1
00
Device class specified by interface
5
bDeviceSubClass
1
00
Device subclass specified by interface
6
bDeviceProtocol
1
00
Device protocol specified by interface
7
bMaxPacketSize0
1
8
Endpoint zero Size = 8 bytes
8
idVendor
2
0d8c
Vendor ID
10
idProduct
2
0012
Product ID
12
bcdDevice
2
0100
Device compliant to the Audio Device Class specification
version 1.00
14
iManufacturer
1
01
Index of string descriptor describing manufacturer
15
iProduct
1
02
Index of string descriptor describing product
16
iSerialNumber
1
00
Index of string descriptor describing the device’s serial
number
17
bNumConfigurations
1
01
Configurations number = 1
Configuration Descriptor
CM108B
USB Audio Single Chip
Datasheet Revision: 1.11 www.cmedia.com.tw
Page 12 / 24 Copyright© C-Media Electronics Inc.
Offset
Field
Size
Value (Hex)
Description
0
bLength
1
09
Total 9 Bytes
1
bDescriptorType
1
02
Configuration Descriptor
2
wTotalLength
2
XXXX
Total length of data returned for this configuration:
Programmable by MSEL and MODE pin
4
bNumInterfaces
1
04
Number of interfaces supported by this Configuration:
0: control interface 1: ISO-OUT interface
2: ISO-IN interface 3: INT-IN(HID) interface
5
bConfigurationValue
1
01
Configuration value
6
iConfiguration
1
00
Index of string descriptor describing this configuration
7
bmAttributes
1
80
Bus Power and support Remote Wakeup
8
bMaxPower
2
32
Maximum power consumption of the USB Device: 100mA
7.1.2 USB audio topology diagram for speaker
Device Descriptor
Offset
Field
Size
Value (Hex)
Description
0
bLength
1
12
Descriptor length
1
bDescriptorType
1
01
Device Descriptor
2
bcdUSB
2
0110
USB 1.1 compliant
4
bDeviceClass
1
00
Device class specified by interface
5
bDeviceSubClass
1
00
Device subclass specified by interface
6
bDeviceProtocol
1
00
Device protocol specified by interface
7
bMaxPacketSize0
1
08
Endpoint zero packet size
8
idVendor
2
0d8c
Vendor ID
10
idProduct
2
0012
Product ID
12
bcdDevice
2
0100
Device release number
14
iManufacturer
1
01
Index of string descriptor describing manufacturer
15
iProduct
1
02
Index of string descriptor describing product
16
iSerialNumber
1
00
Index of string descriptor describing serial number
17
bNumConfigurations
1
01
Number of configuration
Configuration Descriptor
Offset
Field
Size
Value (Hex)
Description
0
bLength
1
09
Descriptor length
1
bDescriptorType
1
02
Configuration Descriptor
2
wTotalLength
2
XXXX
Total length of data returned for this configuration:
Programmable by MSEL and MODE pin
4
bNumInterfaces
1
03
Number of interfaces supported by this Configuration:
00: Control
01: ISO-Out
02: INT-IN (HID)
5
bConfigurationValue
1
01
Configuration value
6
iConfiguration
1
00
Index of string descriptor describing this configuration
7
bmAttributes
1
80
Attributes(PWRSEL=0:Bus Powered, 1:SELF Powered)
8
bMaxPower
1
32
Maximum power consumption from bus = 100mA
0X01
IT
0X09
FEA
0X06
OT
CM108B
USB Audio Single Chip
Datasheet Revision: 1.11 www.cmedia.com.tw
Page 13 / 24 Copyright© C-Media Electronics Inc.
7.1.3 Content format for EEPROM (93C46)
Each address has 2-byte data, prefix `0x` means hex number
Address(Hex)
Description
0x00
bit[15:4] Magic Word
0x670X where X = bit 4, 3, 2, 1
bit[3] The value within address 0x2A, 0x2B, 0x32 is valid 1: valid 0: invalid
bit[2] reserved, should be 1
bit[1] serial number enable control 1: enable, 0: disable(default)
bit[0] reserved, should be 1
0x01
VID 2-byte
0x02
PID 2-byte
0x03
Serial number 1st
byte
(bit15-bit8, first
character)
Serial number length
(bit7-bit0)
0x04
~
0x09
Serial number 12-byte
0x0A
Product string 1st
byte (bit15-bit8, first
character)
Product string length
(bit7-bit0) [0x3E->30,0x40->31Char]
0x0B
~
0x19
Product string 30-byte (default: USB Audio Device)
0x1A
Manufacturer string
1st byte
(bit15-bit8, first
character)
Manufacturer string length
(bit7-bit0) [0x3E->30,0x40->31Char]
0x1B
~
0x29
Manufacturer string 30-byte (default: C-Media Electronics Inc.)
0x2A
bit[15: 9] DAC initial volume (7-bit, default = -10dB)
bit[8: 3] ADC initial volume (6-bit, default = 8dB)
bit[2] DAC EEPROM MAX/MIN volume valid
bit[1] ADC EEPROM MAX/MIN volume valid
bit[0] AA EEPROM MAX/MIN volume valid
0x2B
bit[15:11] AA initial volume (5-bit, default = -7dB)
bit[10] Reserved, should be 0
bit[9] Boost mode 0: 22dB 1:12dB (default)
bit[8] Shout down DAC analog circuits 1: shoutdown, 0: active(default)
bit[7] Total Power Control 1:enable, 0:disable(default)
bit[6] Reserved, should be 0
bit[5] MIC High Pass Filter 1:enable(default), 0:disable
bit[4] MIC PLL Adjust 1:enable, 0:disable(default)
bit[3] MIC BOOST 1:enable (default), 0:disable
bit[2] DAC Output Terminal property set to SPK or HP
1: Headset, 0: Speaker(default) bit[1] HID, 1: enable (default), 0: disable
bit[0] Remote wakeup, 1:enable, 0:disable(default)
0x2C
bit[15:0] DAC Minimum Volume (0xD300, DAC-Min.=-37dB, default=-37dB)
0x2D
bit[15:0] DAC Maximum Volume (0x0000, DAC-Max.=0dB, default=0dB)
0x2E
bit[15:0] ADC Minimum Volume(0xEA00, ADC-Min.=-22dB, default=-12dB)
0x2F
bit[15:0] ADC Maximum Volume(0x1700, ADC-Max.=+23dB, default=+23dB)
0x30
bit[15:0] AA Minimum Volume (0xE900, AA-Min.=-23dB, default=-23dB)
0x31
bit[15:0] AA Maximum Volume (0x0800,AA-Max.+8dB, default=+8dB)
0x32
EE_OPTION2 Register
bit[3] Reserved, should be 0
bit[2] Reserved, should be 0