Reverse-engineering RS485/Mechatrolink-II front-end design
two receivers: my guess is since mechatrolink ii comes in two flavours - 4Mbps and 10MBps, they are probably just doing some filtering in one of the receiving paths.

funny, i also spent some time reverse engineering it about a year ago and then suspended the project. just yesterday decided to revisit it..
back then i captured some dumps from the bus without any isolation, just plugged it directly into rs485 receiver. it worked, but there were some noise when a drive turns on...