To operate the core at a single line speed, set the appropriate bit in the speed capability register, clearing the other three bits. For example, to set a static line rate of 1,228.8 Mb/s, set the speed capability register to 000 0000 0000 0010. Alternatively, the line rate radio buttons in the GUI can be deselected to leave only the desired line rate. This has the effect of presetting the capability register.