Dedicated circuitry on Mercury^™, Stratix^™, and Stratix^™ GX devices that helps to prevent reflections, and as a result, improves signal integrity. The OCT circuitry provides parallel and series termination for single-ended I/O standards, such as HSTL or SSTL-2, and differential termination for differential I/O standards, such as LVDS and LVPECL.