ECN424J600 MAC address coming up zeros
We have been making products with various Microchip devices for 26 years. A current Ethernet product has been in production for 4 years and thousands have been sold. This product has three ECN424J600-I/PT chips. We never have had an issue until now. Our problem is chips from two batches are coming up with all zeros for MAC address (00-00-00-00-00-00). The documentation indicates that each chip has a unique MAC addresses. We have replaced the bad chips with chips from a different mfg batch and they work perfectly (all have unique MAC addresses).
To test if system was reading registers properly, I wrote random numbers into MAC registers MAADR1,2 & 3 on a bad chip. Our system read them correctly as well as all the rest of the special registers. Therefore, there doesn't seem to be a problem reading the chips. Also, since MAC addresses cannot be permanently changed, upon reboot, our system again, read all zeros.
On two different instances, a batch of chips from our supplier have zeros for MAC addresses. They are Batch # 1630J5M & Batch # 1633J34
Good chips, with unique MAC addresses from the same supplier, came from batch # 1737J2S. Of course, we have used many other “Good” batches in the past, but did not log those numbers.
Has anyone else reported this issue?
Would you have any ideas on how to solve this?
Is there possibly a documented list of lot numbers that has all zeros as the MAC address?
Does Microchip manufacture special ECN424J600 chips that have the MAC addresses set to 00-00-00-00-00-00?