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Re: [Fwd: Re: 20 MHz clock oscillator]



Hi,

I've made a test with a CISCO catalyst 2950 and I have no errors.
The same test with a D-LINK DES 1024D give 90 frame errors.

I've visualized the Rx signals with a differential probe ans it's 
difficult to
see a difference of signal quality.

I'd like to understand why the design is so sensitive to the type of switch.

Claude



Mikael Starvik a ้crit:

>The frame counter counts the number of alignment errors. 
>An alignment error occurs when an uneven number of nibbles
>have been received. As far as I can understand tt least 
>two things can cause this to occur:
>
>1. The packaet contains an uneven number of nibbles
>(as interpreted by the receiver).2
>2. A collision occurs at an uneven nibble boundary when
>receiving.
>
>So for a half-duplex network with > 2 nodes it is completely
>normal to get alignment errors (because collisions do happen
>at uneven nibbles).
>
>I will check more with the ASIC guys about this.
>
>/Mikael
>
>-----Original Message-----
>From: owner-dev-etrax@xxxxxxx.com">mailto:owner-dev-etrax@xxxxxxx.com] On Behalf Of girerd
>Sent: Friday, July 02, 2004 5:46 PM
>To: dev-etrax
>Subject: [Fwd: Re: 20 MHz clock oscillator]
>
>
>  Hi,
>
>We use a MCM2+8 in our design and we observed that frame counter
>(field frame in the status return by ifconfig) increases
>during data transfer betwwen a PC and our device. 
>
>here is a sample of result of ifconfig :
>
>ifconfig
>eth0      Link encap:Ethernet  HWaddr 00:40:8C:00:00:C3  
>          inet addr:172.16.5.255  Bcast:172.16.255.255  Mask:255.255.0.0
>          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
>          RX packets:724 errors:0 dropped:0 overruns:0 frame:2
>          TX packets:277 errors:0 dropped:0 overruns:0 carrier:0
>          collisions:0 txqueuelen:100 
>          RX bytes:729894 (712.7 kb)  TX bytes:30094 (29.3 kb)
>          Interrupt:17 DMA chan:1 
>
>lo        Link encap:Local Loopback  
>          inet addr:127.0.0.1  Mask:255.0.0.0
>          UP LOOPBACK RUNNING  MTU:16436  Metric:1
>          RX packets:35 errors:0 dropped:0 overruns:0 frame:0
>          TX packets:35 errors:0 dropped:0 overruns:0 carrier:0
>          collisions:0 txqueuelen:0 
>          RX bytes:3804 (3.7 kb)  TX bytes:3804 (3.7 kb)
>
>
>What is the exact meaning of the field frame in the status return by ifconfig ?
>
>Does someone has any idea about the possible reasons of this value of frame ?
>
>
>Thank you
>
>Claude
>
>
>
>
>  
>

-- 
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