USS-720Instant USB

Preliminary Data Sheet, Rev. 5

USB-to-IEEE1284 Bridge

September 1999

 

 

USB Port (continued)

The format for the externally supplied data is as shown in Table 2. The addressing for the specified EEPROM device is word aligned, so the following restrictions are placed upon the starting locations for the configuration and string descriptors.

The configuration descriptor must start at word address 0x13 (byte address 0x26).

String descriptors must start at an address that is aligned on a double-word boundary.

Table 2. Externally Supplied Data Format

Byte Address

Word Address

Value

 

 

 

0x00

0x00

0x12

0x01—0x12

Device descriptor as defined in USB Specification Revision 1.0.

0x26

0x13

Total length of string to be returned in response to a

 

 

GET_CONFIGURATION_DESCRIPTOR request.

0x27—0x2F

Configuration descriptor as defined in USB Specification Revision 1.0.

0x30—???*

Interface and endpoint descriptors to be returned in response to a

 

 

GET_CONFIGURATION_DESCRIPTOR request.

Any even word

address beyond

Length of string to return in response to a GET_STRING_DESCRIPTOR

the end of the configuration

request. This address divided by two should be included in the low byte of the

descriptor return string.

wIndex field of the GET_DESCRIPTOR standard command.

Next address—end of string

String descriptor as defined in USB Specification Revision 1.0.

descriptor.

 

 

*The question marks (???) indicate that this byte address value is determined for the user’s application based on the above information. The number is going to vary depending on how the user formats their configuration information.

Note: Tables 3—14 describe the descriptor data contained in the USS-720’s internal ROM. This information can be used as a guide in creating the externally supplied descriptor data.

Onboard Device Descriptor

There is only one device descriptor for each USB device. This descriptor contains the definitions of the device class and the device subclass, among other things.

Table 3. Device Descriptor

Offset

Field

Size

Value

Description

 

 

 

 

 

0

bLength

Byte

0x12

Size of this descriptor in bytes.

 

 

 

 

 

1

bDescriptorType

Byte

0x01

Device descriptor type.

 

 

 

 

 

2

bcdUSB

Word

0x0100

USB Specification release number in BCD.

 

 

 

 

 

4

bDeviceClass

Byte

0x00

Interface specific. See Tables 6, 8, and 11.

 

 

 

 

 

5

bDeviceSubClass

Byte

0x00

Interface specific. See Tables 6, 8, and 11.

 

 

 

 

 

6

bDeviceProtocol

Byte

0x00

Interface specific. See Tables 6, 8, and 11.

 

 

 

 

 

7

wMaxPacketSize0

Byte

0x08

Maximum packet size for endpoint 0.

 

 

 

 

 

8

idVendor

Word

0x047E

Vendor ID for Lucent Technologies.

 

 

 

 

 

10

idProduct

Word

0x1001

Product ID.

 

 

 

 

 

12

bcdDevice

Word

0x0103

Device release number in BCD.

 

 

 

 

 

14

iManufacturer

Byte

0x00

Index of string descriptor describing manufacturer.

 

 

 

 

 

15

iProduct

Byte

0x00

Index of string descriptor describing this product.

 

 

 

 

 

16

iSerialNumber

Byte

0x00

Index of string descriptor describing the device’s serial number.

 

 

 

 

 

17

bNumConfigurations

Byte

0x01

Number of possible configurations.

 

 

 

 

 

5-6

Lucent Technologies Inc.

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Lucent Technologies USS-720 manual USB-to- Ieee 1284 Bridge September, Onboard Device Descriptor