XR

22404

9/14

REV1A

Applications Information (Continued)

External EEPROM

downstream ports. The contents of the EEPROM are described in Table 2. In order for contents of the EEPROM to be

used by the XR22404, both the EEPROM check values at address 0x00, 0x01 and the checksum at address 0x1F must be

correct. If either field is incorrect or reserved fields are not set to 0x00, the EEPROM contents will be ignored and the device

will use the default descriptor values.

Table 2. EEPROM Contents

Address

Content

Description

0x00

0x40

EEPROM check value.

0x01

0x1A

EEPROM check value.

0x02

Vendor ID, LSB

idVendor field LSB of device descriptor.

0x03

Vendor ID, MSB

idVendor field MSB of device descriptor.

0x04

Product ID, LSB

idProduct field LSB of device descriptor.

0x05

Product ID, MSB

idProduct field MSB of device descriptor.

0x06

Device Release, LSB

bcdDevice field LSB of device descriptor in binary coded decimal format.

0x07

Device Release, MSB

bcdDevice field MSB of device descriptor in binary coded decimal format.

0x08 to 0x19

Reserved

Must be 0x00.

0x1A

Downstream Ports

Number of downstream ports in the bNbrPorts field of the hub descriptor.

0x1B to 0x1E

Reserved

Must be 0x00.

0x1F

Checksum

Bitwise checksum of EEPROM values from address 0x00 to 0x1E.