Lpc2000

Hi Joel

I haven´t experienced this problem but if a powerful Coldfire gets 
overloaded then the NE64 will certainly also have problems.
It is possible to specifically block ARP frames in the hardware 
filter so that they don´t disturb but this would mean that other 
devices on the network wouldn´t be able to find the NE64 since it 
would not be able to react to ARP requests. If this can be 
tolerated, the filer could be deactivated for the time the NE64 is 
resolving local addresses, but it makes for a very special solution 
rather than a general one.
Arp frames themselves are not very demanding since most can be 
ignored if the IP address is is not equal to the local one (although 
a local ARP table is generally maintained which includes all network 
activity seen).
I have always understood that general broadcast frames cause most 
overloading problems and it also certainly helps to not operate in 
promiscuous mode on a network with high foreign activity levels.
Using switches to shield weaker devices can also help.
However at the end of the day there are real limits. If frames have 
to be handled, this requires time and if the frame rate is faster 
than the throughput then something will inevitably get lost. If a 
100M LAN is really operating at the limit, each byte should be 
processed in about 80ns and that requires a certain level of power.
It is difficult to say where the limit for a particular application 
in a particular network lies but it doesn´t make much sense to 
connect a NE64 in promiscuous mode next to a Cisco router - probably 
neither a Coldfire. For many other jobs they are nevertheless fine.

Cheers

Mark
www.mjbc.ch


--- In lpc2000@yahoogroups.com, "Joel Winarske" <joelw@i...> wrote:
>
> Hello Mark,
> 
> > - For low-range embedded Internet applications the MC9S12NE64 is 
king.
> > PCB design is extremely simple and a double layer board works 
fine,
> > even when using all peripherals - see some photos at
> > http://www.mjbc.ch/pics/uTasker/uTasker1_eng.html (if only 
SPI/LAN is
> > required, it can almost fit under a standard RJ45 connector)
> 
> I've experienced networks that brought high powered Coldfire based 
solutions
> to their knees due to level of ARP traffic.  How does the 
MC9S12NE64 respond
> with abnormally high ARP traffic?
> 
> On the upcoming LPC Ethernet solution I really hope they spend 
some extra
> effort on Ethernet hardware filtering and IP hardware checksum via 
DMA.
> 
> Joel
>