Disclosed is a novel structure and process for detecting protocol errors on a communications bus. After the shallow trench is filled with the dielectric material and planarized, a top portion of the hard mask is removed, resulting in a top portion of the filled dielectric material to protrude above the remaining hard mask. A voltage comparator circuit coupled to the output node and the transistor is configured to generate the control signal to control coupling and decoupling of the output node and the voltage supply through the transistor based on a voltage of the output signal relative to the reference voltage.