tqm 8260 scc ethernet crc errors
thomas.geffert at keymile.com
Fri Nov 1 23:22:53 EST 2002
I've problems with receiving packets with an TQM8260 board on the SCC
10Mbit ethernet interface.
If I connect two tqm boards directly via an ethernet crossover cable and
send udp packets from one board to another the receiving CPM marks
1-15% of all packets with an crc error flag (this depends on packet
size and send speed). When I check the udp checksum of the received
packets this check only ails for approx 5-10% of the marked packets,
Send packets in 5s CPM says CRC-Error UDP checksum error
6000 (512 bytes each) 591 / 9.8% 94 / 1.6%
4850 (512 bytes each ) 220 / 4.5% 34 / 0.7%
6000 (128 bytes each) 182 / 3% 43 / 0.7%
The faster the packets are send and the longer the packets are the more errors
are detected. If I send the packets with a rate <50 packets/s I got almost
no crc errors.
I'm very surprised over the errors, as I use a direct connection
between the boards and send only in one direction. In such a case I
would expect to get no errors. Can this be an EMI error of the
physical SCC ethernet interface of the tqm boards?
I also connected the tqm board via a switch to a PC 10Mbit ethernet
interface and got slightly smaller error rates, but they are still
there. If I use the FCC ethernet interface I don't get this problems.
Did anyone make similiar experiences or has an idea how this errors can happen?
I use the DENX linux-2.4.4-2002-10-06 (patched for RTAI linux 24.1.10)
and enabled full duplex mode in the SCC enet.c driver (without full
duplex I got also crc errors and lots of dropped packets).
 I got this value from the scc1 parameter ram field crcec.
Dipl.-Ing. Thomas Geffert
KEYMILE / Datentechnik Intercom GmbH
Frankenring 14, 30855 Langenhagen, Germany
Tel +49 (0)511 978197-669 / Fax +49 (0)511 978197-670
mailto:thomas.geffert at keymile.com / http://www.keymile.com
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