EIO1616MT extension module is the EtherCAT used by the extension module Bus Controller. When I/O and other resources are insufficient, extension module need to be added. The controller can connect multiple extension module at the same time. Extension module is connected through the bus, each extension module has a unique address, starting from 0. The program on the controller can access resources on the extension module by using the IO Number. The IO number is set by the bus instruction NODE_IO.