An apparatus including a handshake window enabler having a pair of differential inputs and a window enablement output, a common mode detector coupled to a power input and a ground input and having a handshake inhibit output, and a handshake disabler coupled to the handshake window enabler, the common mode detector, and the pair of differential inputs. If a common mode voltage that out of range (“too high”) is detected, high speed handshake protocols are such that the bus operates a lower data rate.