LAN9500AI datasheet(137/213 Pages) MICROCHIP

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DS00001875A-page 137

LAN950x

30:28

EPC Command

This field is used to issue commands to the EEPROM controller. The EPC

will execute commands when the EPC Busy bit is set. A new command must

not be issued until the previous command completes. This field is encoded

as follows:

000 = READ

001 = EWDS

010 = EWEN

011 = WRITE

100 = WRAL

101 = ERASE

110 = ERAL

111 = RELOAD

READ (Read Location): This command will cause a read of the EEPROM

location pointed to by EPC Address. The result of the read is available in the

E2P_DATA register.

EWDS (Erase/Write Disable): After issued, the EEPROM will ignore erase

and write commands. To re-enable erase/write operations, issue the EWEN

command.

EWEN (Erase/Write Enable): Enables the EEPROM for erase and write

operations. The EEPROM will allow erase and write operations until the

Erase/Write Disable command is sent, or until power is cycled.

Note:

The EEPROM device will power-up in the erase/write-disabled

state. Any erase or write operations will fail until an Erase/Write

Enable command is issued.

WRITE (Write Location): If erase/write operations are enabled in the

EEPROM, this command will cause the contents of the E2P_DATA register

to be written to the EEPROM location selected by the EPC Address field.

WRAL (Write All): If erase/write operations are enabled in the EEPROM, this

command will cause the contents of the E2P_DATA register to be written to

every EEPROM memory location.

ERASE (Erase Location): If erase/write operations are enabled in the

EEPROM, this command will erase the location selected by the EPC Address

field.

ERAL (Erase All): If erase/write operations are enabled in the EEPROM, this

command will initiate a bulk erase of the entire EEPROM.

RELOAD (Data Reload): Instructs the EEPROM controller to reload the data

from the EEPROM. If a value of A5h is not found in the first address of the

EEPROM, the EEPROM is assumed to be un-programmed and the Reload

operation will fail. The “Data Loaded” bit indicates a successful load of the

data.

Note:

A failed reload operation will result in no change to descriptor

information or register contents. These items will not be set to

default values as a result of the reload failure.

R/W

000b

27:11

RESERVED

Bits

Description

Type

Default

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