OpenCores 10/100 MAC reports InvalidSymbol

[Altera_Forum]

I've built a system with the opencore ethernet MAC connected to the PHY port# 5 of the integrated switch KS8995MA. 

I can successfully send packets but received packets are reported by the MAC with the status bit InvalidSymbol. However, a dump of the received frames show that they are correct. I'm not an expert of TimeQuest and haven't constrained correctly the design: could it explain this?

[Altera_Forum]

I have experienced exactly the same problem with 1Gbit MAC. Unfortunately I still do not have a solution. My current theory is that it is because I have not properly constrained the rgmii tx interface. This is not done for you by the MAC.  

 I have been able to reduce the number of 'invalid symbols' by changing the output delay on the tx data/control lines relative to the tx clock however I do not really understand why/how this is the case.  Sorry I cannot offer any advice. I will reply when I get to the bottom of my problem

[Altera_Forum]

Ok, thanks for your reply. 

I finally decided to switch to the TSE that I use in 10/100 mode only. The board had a hardware issue (RX_ERR was not connected) that make me loose a lot of time, but it works now.

[Altera_Forum]

Its good to hear that you resolved your receive errors. For me too I found a hardware fault to be the cause of the invalid symbols. A power supply issue with the 2.5V analogue PHY/Magnetics supply was causing transmission errors.