I am troubleshooting a problem with a product that uses the W5100 and an ATmega CPU to implement a Modbus/TCP server. I think noise glitches are getting into W5100 reset line, causing loss of communication.
Strangely, it still responds to ping messages, but stops responding to TCP messages or connection requests. A sanity check of reading back the MAC address from W5100 shows the address is okay, but still suspect noise on reset line, or possibly SPI bus.
A couple questions:
Could an extremely short glitch on reset line (shorter than 2usec) affect only a part of the W5100 and not another part?
If I do a reset and reconfigure it to make it recover, is doing a soft reset just as good as doing a hard reset? Does a hard reset do something not done by a soft reset?
Any thoughts are appreciated,