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RE: packet drops in the ETRAX100LX ethernet


The older model "AXT6212 17854 A0147" is mask revision 2 
and the newer   "AXT6212 18816 A0214" is mask revision 3.

The differences between the two versions of ETRAX 100LX (part numbers
17854 and 18816) are limited to small changes in the USB interface,
and there are no design related differences that could effect the
Ethernet operation.

We have performed extensive Ethernet communication testing on both 
mask revisions. The specific batch A0214 have been used in some of 
these tests. No problems have been observed. 

There may be some batch dependent variations in parameters like power
consumption, signal threshold levels and output buffer speed, due to
normal process variation. This kind of variation is taken into account 
in the specification of ETRAX 100LX, and should not cause any problems 
in a properly designed circuit.

The problems you describe indicate that there is something marginal in 
the design of the circuit board, that makes it sensitive to batch
variation. Typical problem areas are:

- System clock (20 MHz).
  Jitter, noise and/or improper termination on the clock signal may
  affect the operation of the internal PLL in ETRAX 100LX. Too low 
  amplitude of the system clock (e.g. because of EMI suppression)
  may also result in batch dependent problems. 

- Transceiver clock.

  Crosstalk and/or improper termination of the 25 MHz clock to the 
  transceiver may cause packet loss.

- PLL loop filter.

  Improper layout of the PLL loop filter may introduce noise that
  affects the stability of the internal PLL.

- Insufficient decoupling or improper grounding.

  This may cause batch dependent problems, since variations in power 
  consumption and output buffer speed vill affect the amount of
  ground bounce and power ripple on the board. 

Best regards

Per Zander

-----Original Message-----
From: owner-dev-etrax@xxxxxxx.com]On">mailto:owner-dev-etrax@xxxxxxx.com]On Behalf
Of Kim, Hyojun
Sent: Tuesday, June 04, 2002 4:06 AM
To: dev-etrax
Subject: packet drops in the ETRAX100LX ethernet

Hi all,

I have some problem in the ETRAX100LX ethernet.

I have tested two types of ETRAX100LX chips at the
same PCB and same flash image.
The older model is "AXT6212 17854 A0147",
and newer is       "AXT6212 18816 A0214".

When using OLDER,
the network bootloading is completed just 1~2 seconds,
and there's no packet drops at pinging in the local

But using NEWER,
it takes almost 2~3 minutes in the network
and there's approximately 10% packet drops at pinging
in the local network.

I have tested other chips of the two models,
the result is all the same.


Best Regards,
Hyojun Kim / Cellinx Systems

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