EMI + ENET = disaster

paolo239955_stm1 · ‎2009-07-27

Posted on July 28, 2009 at 08:09

paolo239955_stm1 · ‎2011-05-17

Posted on May 17, 2011 at 09:59

Hi all,

My application with STR912FW44 uses 256K * 16 external RAM. E-Ram is correctly working (I run an accurate test on startup). I use also Ehternet with a small internal Webserver.

The problem is, if I put my heap in external RAM and I start my webserver everything SEEM to work (in pure ST style :-Y), but I miss packets on my client (Wireshark reports [TCP Previous segment lost] [TCP segment of a reassembled PDU]).

If I turn back to internal RAM everything starts to work again (but I need that extra RAM, obviously). How is it possible for external RAM to degradate Ethernet performance ??!? Aren't they on completely different buses ??!

Any help greatly appreciated....

paolo239955_stm1 · ‎2011-05-17

Posted on May 17, 2011 at 09:59

Solved. If you put ENET OperatingMode to 100Mbps the ENET DMA FIFO gets full and misses bytes. With internal RAM (faster) this problems disappears.

Must set ENET OperatingMode to 10Mbps for external RAM storage of packets (or use a faster RAM .....).

WHEW !