Problems with MC9S12NE64 and some switches

Hello!

We are using a MC9S12NE64 for a RS485->Ethernet router. we've
experiencing problems with certain network switches. We get packet
losses when we connect the router to some switches, the packages gets
sent from the MC9S12NE64 but don't end up at the receiver.  But with
other switches the exact same application works fine. If  connect a
network hub between the MC9S12NE64 and the switch the packages get's
through fine.

The problem seems to be related with long packages because messages
that a "small" get through fine. No package is larger then 750 bytes.
Could this be a electric problem with the transmitter in the
MC9S12NE64? Any thoughts you might have would be appreciated.

Best Regards

Johnny Karlsson
KTC Tech

<johnny.karlsson@gmail.com> wrote in message 
news:1145605971.447181.218750@z34g2000cwc.googlegroups.com...
> Hello!
>
> We are using a MC9S12NE64 for a RS485->Ethernet router. we've
> experiencing problems with certain network switches. We get packet
> losses when we connect the router to some switches, the packages gets
> sent from the MC9S12NE64 but don't end up at the receiver.  But with
> other switches the exact same application works fine. If  connect a
> network hub between the MC9S12NE64 and the switch the packages get's
> through fine.
>
> The problem seems to be related with long packages because messages
> that a "small" get through fine. No package is larger then 750 bytes.
> Could this be a electric problem with the transmitter in the
> MC9S12NE64? Any thoughts you might have would be appreciated.

I doubt it's electrical, but I might be wrong.

I'd be inclined to put a packet sniffer on the network segment closest to 
your boards, and see what surprises you get.

ARP issue, maybe?

Steve
http://www.fivetrees.com 

Steve at fivetrees skrev:

> <johnny.karlsson@gmail.com> wrote in message
> news:1145605971.447181.218750@z34g2000cwc.googlegroups.com...
> > Hello!
> >
> > We are using a MC9S12NE64 for a RS485->Ethernet router. we've
> > experiencing problems with certain network switches. We get packet
> > losses when we connect the router to some switches, the packages gets
> > sent from the MC9S12NE64 but don't end up at the receiver.  But with
> > other switches the exact same application works fine. If  connect a
> > network hub between the MC9S12NE64 and the switch the packages get's
> > through fine.
> >
> > The problem seems to be related with long packages because messages
> > that a "small" get through fine. No package is larger then 750 bytes.
> > Could this be a electric problem with the transmitter in the
> > MC9S12NE64? Any thoughts you might have would be appreciated.
>
> I doubt it's electrical, but I might be wrong.
>
> I'd be inclined to put a packet sniffer on the network segment closest to
> your boards, and see what surprises you get.
>
> ARP issue, maybe?
>
> Steve
> http://www.fivetrees.com

Well after investigating the problem More thoroughly i found that the
MC9212NE64 board always have to retransmit, and the retransmitted
packet got through. When i lowered the packet size everything works. So
I'm not shure why but a tcp packet size of 750bytes seems to large for
the switch.