> From what I can gather, the (soldered down) 28C16 EEPROM on the 16500L LAN > card has either been wiped by an errant write, or has 'forgotten' its > contents.
My guess is something is broken rather than the chip has been wiped. Have you checked the chip select or data path? > Does anyone have a dump of the contents of this chip from a working 16500L > card? If it's the MAC address, it's unique to each board. Do you remember the old one? If not, you can either cheat and make one up, or find an old board, use its MAC address, and destroy that board so you can't possibly get a duplicate on the net when that board gets plugged in. In the early Ethernet days, the MAC address was typically stored in a small ROM. Since even the smallest ROM chips available had lots of room they added some other stuff. A description of the format is probably available online and/or you can probably decode it from some driver software that reads the ROM. A MAC address is 6 bytes. I think they added 2 bytes of CRC. A common small ROM was 32x8, so that would have room for 4 copies of an 8 byte MAC address+CRC. I think they had the address, it's inverse, and a couple of test patterns. As silicon marched on, typical TTL ROMs fell off the edge of the world and EEROMs became cheaper. So 32 bytes of data was stored in chips that could hold xK bytes. > Failing that, does anyone know of a way to reprogram the MAC address into > the chip? Some secret key-combination, or other trick? I doubt if there is a simple way. Why would you want to do that? The idea is that each board should have a unique MAC address. You want to make it hard for idiots to do things like copy an address and destroy that uniqueness. The boards typically disabled the write-enable pin. The chips were programmed before getting soldered down. Or maybe they were programmed on the tester which would overdrive a pullup. -- These are my opinions, not necessarily my employer's. I hate spam. _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
