Smsc LAN9512 User Manual download pdf (Page 20)

USB Hub with Integrated 10/100 Ethernet Controller

Datasheet

Revision 1.0 (04-20-09) 20 SMSC LAN9512

DATASHEET

Chapter 3 EEPROM Controller (EPC)

LAN9512 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. A total of nine address

bits are used to support 256/512 byte EEPROMs.

Note: A 3-wire style 2K/4K EEPROM that is organized for 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 EEPROM controller also allows the Host system to read, write and erase the contents of the Serial

EEPROM.

3.1 EEPROM Format

Table 3.1 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 Device Descriptors, the only valid values for the length are 0 and 18.

Note: For Configuration and Interface Descriptors, 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 no Configuration Descriptor is present in the EEPROM, then the Configuration Flags affect

the values of bmAttributes and bMaxPower in the Ethernet Controller Configuration Descriptor.

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

Table 3.1 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

1 2 ... 15 16 17 18 19 20 21 22 23 24 25 ... 45 46

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