By pushing the backplane bus’ speed even further, differential signalisation must be used on the TX and the RX lines all the way ’round, and even more powerful transmission ICs are to be used (for eg. PROFIBUS capable transceivers).
Even with these modifications the transmission speeds hardly can exceed 10 Mbps.
One of which is EtherCAT, which is far the most speedy and efficient network type.
Since it uses ethernet physical layer, its speed is fixed 100 Mbps, and its “data insert on the fly” method guarantees an ultimately high performance compared to other fieldbus systems.
For space limitation and cost reduction reasons the connectors are 6 pole ones, where 4 of them are for signal transmission, the rest 2 are for the +5V backplane supply. This +5V is for the ASICs only, the more power hungry I/Os has to be fed through the sperarte +24V input connector (at the card’s front panel). This also provides the electrical isolation between the backplane bus and the I/Os (usually the I/Os are also isolated from the backplane using optocouplers).
Here is an example topology:
For high speed transmission an ethernet based approach is the best choice.