LAN9500A datasheet(26/66 Pages) SMSC

26 / 66 page

USB 2.0 to 10/100 Ethernet Controller

Datasheet

Revision 1.1 (04-18-13)

SMSC LAN950x Family

DATASHEET

Chapter 5 EEPROM Controller (EPC)

LAN950x may use an external EEPROM to store the default values for the USB descriptors and the

MAC address. The EEPROM controller supports most “93C46” type EEPROMs. The EEP_SIZE strap

selects the size of the EEPROM attached to the device. When this strap is set to “0”, a 128 byte

EEPROM is attached and a total of seven address bits are used. When this strap is set to “1” a

256/512 byte EEPROM is attached and a total of nine address bits are used.

Note: A 3-wire style 1K/2K/4K EEPROM that is organized for 128 x 8-bit or 256/512 x 8-bit operation

must be used.

The MAC address is used as the default Ethernet MAC address and is loaded into the MAC’s ADDRH

and ADDRL registers. If a properly configured EEPROM is not detected, it is the responsibility of the

Host LAN Driver to set the IEEE addresses.

After a system-level reset occurs, the device will load the default values from a properly configured

EEPROM. The device will not accept USB transactions from the Host until this process is completed.

The device’s EEPROM controller also allows the Host system to read, write and erase the contents of

the Serial EEPROM.

5.1

EEPROM Format

Table 5.1 illustrates the format in which data is stored inside of the EEPROM.

Note the EEPROM offsets are given in units of 16-bit word offsets. A length field with a value of zero

indicates that the field does not exist in the EEPROM. The device will use the field’s HW default value

in this case.

Note: For the device descriptor, the only valid values for the length are 0 and 18.

Note: For the configuration and interface descriptor, the only valid values for the length are 0 and 18.

Note: The EEPROM programmer must ensure that if a string descriptor does not exist in the

EEPROM, the referencing descriptor must contain 00h for the respective string index field.

Note: If all string descriptor lengths are zero, then a Language ID will not be supported.

Table 5.1 EEPROM Format

EEPROM ADDRESS

EEPROM CONTENTS

00h

0xA5

01h

MAC Address [7:0]

02h

MAC Address [15:8]

03h

MAC Address [23:16]

04h

MAC Address [31:24]

05h

MAC Address [39:32]

06h

MAC Address [47:40]

07h

Full-Speed Polling Interval for Interrupt Endpoint

08h

Hi-Speed Polling Interval for Interrupt Endpoint

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