LAN91C111 problem?

Hi

I have a design based more or less on the Stratix dev board with an Ethernet driver which is a modified version of Altera's device driver.

To test the quality/performance of the Ethernet link I uses a ping utility that can execute ping cycles continuously without idle delay.

My problem is that ping packets (any IP packet in fact) are lost without a trace. No error indication or receive overrun is reported by LAN91C111.

If my target transmits nothing except for ICMP replies, the packet loss is only 1 per mill pings. If my target transmits UDP packets continuoysly however, the ping loss is 1 per 10/100 packets.

My setup is full duplex. No DMA, Interrupt driven. I'm pretty sure that my target receives all packets as I have connected a PC in paralell to the same hub as my target is connected to. Etherreal receives all ping packets, my target don't.

The problem is not related to the stack as I count ICMP req's in the Ethernet driver and sees the packet loss here.

I see receive overrun from time to time when I overload my target, so it's working fine (and yes, I have enabled the interrupt).

So it all comes down to: Is the lost it due to a FIFO full condition or not. I mean, the chip can't just discard packets without reporting it?