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Ethernet controller hangs?

Hi everyone!

Remember me?
I'm the guy with two OS-less Device Server Platforms passing
data from one LAN to another on a 422 link.

I've got this problem.
Everything runs fine most of the time, but every once in a while
the communication fails.  In one direction.

I've got two machines, labelled "Inside" and "Outside":

LAN1 ---- "Inside" -- 422 -- "Outside" ---- LAN2

What happens is that the data going from LAN2 to LAN1
suddenly stops flowing, but at the same time the data going
from LAN1 to LAN2 continues as normal.
In other words, the software hasn't hung.

If I disconnect the "Inside" LAN1 connection and then reconnect
it, normal function resumes, ie. data flows in both directions.
The software does not check the Ethernet controller status and
does not handle any negotiations for link speed or anything
like that, so it is not affected by the unplugging / replugging.

Now my question is: is it possible that the Ethernet controller has
partially hung (sending part) and is reset when the cable is plugged
back in?

Is it possible that the RS422 controller has partially hung (receiving
part) and is reset when the Ethernet cable is plugged back in?

I realise that it is still by no means impossible for this to be a software
error, but I thought I'd explore this avenue as well.


/Uffe Sjöstedt
SaabTech Systems AB