EEPROM with dynamic contents.

[allsey87]

Hi All,

I have an interesting problem that I'm trying to find an innovative solution for.

I have USB to Ethernet,USB,USB chip (**broken link removed**) that gets all of it's configuration from an attached EEPROM (it also supports a default configuration if the EEPROM is not detected or not of a valid format). For the LAN9512 a 3-wire style 2K/4K EEPROM that is organized for 256/512 x 8-bit operation must be used.

I would like to effectively configure some of these memory locations on the EEPROM from the main processor which is on the same board as the LAN9512.

I'm thinking that I might use a dual port EEPROM that I can configure from the host processor before issuing a soft reset to LAN9512 to reload the internal registers from the EEPROM. For this I would ideally need a dual port EEPROM that matches the criteria above while providing both a 3-wire interface for the LAN9512 and a i2c interface for my host processor.

Other solutions could involve emulating an EEPROM device using a microcontroller or FPGA, although this solution is not as attractive as I would need store the configuration image or bitstream of the emulating device somewhere on board. This approach also seems like a page out of a book titled "overkill 101".

Any thoughts?

 

[123jack]

Sorry I can't see what you have a problem with?

 

[allsey87]

@123jack, not every post on EDAboard is a problem as such. In this case I have what I think will be a working solution to my problem and am curious whether any alternatives exist...

I have concluded so far that the best option is to use a multiplexer on the EEPROM. The multiplexer select lines are pulled up/down to by default connect the EEPROM to the processor and assert the reset line on the lan9512. When the driver is loaded on the microprocessor, the EEPROM is checked/updated with the correct values before overriding the select lines to redirect the pins of the EEPROM to the microprocessor and deasserting the reset line.

 

[123jack]

OK fair enough but I still cant see what anyone can say. I dont see anything to comment on.
Maybe I'm just being slow on the uptake here.