SMSC LAN9420 - Manual (Page 35)

Single-Chip Ethernet Controller with HP Auto-MDIX Support and PCI Interface
Datasheet
SMSC LAN9420/LAN9420i 35 Revision 1.22 (09-25-08)
DATASHEET
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.
Figure 3.10 EEPROM EWDS Cycle
Figure 3.11 EEPROM EWEN Cycle
0
EECLK
EEDIO (INPUT)
EEDIO (OUTPUT)
EECS
1 0 0 0
t
CSL
0
EECLK
EEDIO (INPUT)
EEDIO (OUTPUT)
EECS
1 0 1 1
t
CSL