A controller, in particular an Ethernet controller has a control unit operable to receive commands and data through an I/O interface; a plurality of registers arranged in a register block which is divided into a plurality of register banks, wherein at least one register controls a function of the controller; a register address unit having logic for accessing one of the plurality of registers by a plurality of addressing schemes, wherein the addressing schemes at least has a direct address provided by received data, a combined address provided by a partial address from a received command and a bank address stored in a bank register, and an address selected form a plurality of predetermined addresses through a received command.