Ethernet interconnection between two embedded PC's inside one box

If both embedded PCs have the same potential (GND to GND = 0 Volt) and the distance is "short" then: *) You can drop both PHY and wire MAC to MAC.

If potentials differ or the distance is too long. Then you can: *) Remove one magnetics transformer.

This ofcourse requires that all persons handling the equipment are aware of this issues when handling units or expanding them. Ie a motor drive on one of them may make the first solution unsuitable. The second solution requires that the network wire isn't reconnected to any other unit that is also unisolated.

Bert,

Can these two PCs connect to each other by a hub or switch ??

If so then a cross over cable will work just fine.

donald

^^^^^ Sounds a bit cheesy to me.

Much of Ethernet's cost is in the interface to that unshielded twisted long wire.. You can omit transformers and such, but... why Ethernet at all? Multiprocessor communication is usually through shared (two-port) RAM, isn't it? Or even a pair of FIFO RAMs?

I'd either use a standard processor board with the full Ethernet hardware, and treat the ports as useful for breaking out signals for maintenance, OR go with a full-custom shared memory.

I understand that there arte better solutions for communication between two PC's, but in this system we have not the opportunity to chose another interface. Ethernet is the only available interface. Thank you all for your suggestions !!!