C371346_375F2440A66FD1C882296D07948AE54C.pdf - 第12页

CM108AH

Highly Integrated USB Audio I/O Controller

www.cmedia.com.tw

7 Function Description

7.1 USB Interface

The CM108AH 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 CM108AH, 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 serial number for

each set. The CM108AH automatically detects the 93C46, and the overwrite function is performed at start up.

7.1.1 Device Descriptors

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

5

bDeviceSubClass

1

00

6

bDeviceProtocol

1

00

7

bMaxPacketSize0

1

40

Endpoint zero size = 64 bytes

8

idVendor

2

0d8c

Vendor ID

10

idProduct

2

0139

Product ID programmable by MSEL and MODE pin

12

bcdDevice

2

0100

Device compliant with Audio Device class

specification version 1.0

14

iManufacturer

1

01

String descriptor index describes manufacturer

15

iProduct

1

02

String descriptor index describes product

16

iSerialNumber

1

03

String descriptor index displays device serial no.

17

bNumConfigurations

1

01

Configuration number = 1

CM108AH

Highly Integrated USB Audio I/O Controller

www.cmedia.com.tw

7.1.2 Configuration Descriptors

Offset

Field

Size

Value (Hex)

Description

0

bLength

1

09

Total: 9 bytes

1

bDescriptorType

1

02

Configuration descriptor

2

wTotalLength

2

Total length of data returned for this configuration,

programmable by MSEL and MODE pin

4

bNumInterfaces

1

04 or 03

Number of interfaces supported by this configuration,

changed by MODE pin:

EP0: control interface

EP1: ISO-OUT interface

EP2: ISO-IN interface (optional)

EP3: INT-IN (HID) interface

5

bConfigurationValue

1

01

6

iConfiguration

1

00

7

bmAttributes

1

A0 or E0

Programmable by PWRSEL

8

bMaxPower

2

32 or FA

Maximum power consumption of the USB,

programmable by MODE and PWRSEL pins

CM108AH

Highly Integrated USB Audio I/O Controller

www.cmedia.com.tw

7.1.3 Content Format for EEPROM (93C46)

Addr

(Dec)

Addr

(Hex)

Description

0

0x00

Magic Word

0x670X where X = bit 4, 3, 2, 1

bit 3, value within address 0x2A,0x2B is valid 1: valid 0: invalid

bit 2, manufacture string enable 1: enable(default) 0: disable

bit 1, serial number enable control 1: enable 0: disable(default)

bit 0, product string enable control 1: enable(default) 0: disable

1

0x01

VID 2-byte

2

0x02

PID 2-byte

3

0x03

Serial number length (low byte)

Serial number first byte (high byte)

4

~

9

0x04

~

0x09

Serial number: 12 bytes

10

0x0A

Product string length (low byte)

Product string first byte (high byte)

11

~

25

0x0B

~

0x19

Product string: 30 bytes (default: USB PnP sound device)

26

0x1A

Manufacturer string length

(low byte)

Manufacturer string first byte

t

(high byte)

27

~

41

0x1B

~

0x29

Manufacturer string: 30 bytes (default: C-Media Electronics Inc.)

42

0x2A

bit 15 ~ 8 DAC initial volume (7-bit) max: 0x02 min: 0x4a

bit 7 ~ 0 ADC initial volume (5-bit) max: 0x00 min: 0x78

43

0x2B

bit 15 ~ bit 9 <reserved>

bit 8 Shutdown DAC analog - 1: shutdown, 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 ADC synchronization mode - 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 enable/disable

1: enable, 0: disable (default)

44

~

END

0x2C

~

END