Quiet operation is another feature in favor of R8C MCUs. The MCUs are designed to generate low levels of electromagnetic interference (EMI) for conformance to noise regulations. They also have low electromagnetic susceptibility (EMS) to operate reliably in noisy environments addressing issues that are major design concerns in today's embedded applications. Design techniques used to reduce EMI and EMS issues also save costs by eliminating the external filter and protection devices required by MCUs with poorer EMI or EMS performance. One of the EMS reduction techniques is careful power and ground layout. The Vcc and Vss pins are physically separated by a signal pin to reduce noise pickup on the power and ground wiring. Also, parasitic capacitance is built into the MCU between the Vcc and Vss connections to filter out the effects of noise radiated by external sources. Another EMS reduction technique is to put key input signals through protection circuits and noise filters before they are connected to the MCU's internal logic circuits. As a result, R8C devices cope well with static electricity and have safeguards against inadvertent circuit latch ups. To minimize the EMI radiated by the MCU, the output impedance of the transistors in buffer circuits is matched to the characteristic impedance of circuit board wiring. As a result, signal waveforms are cleaner, with less ringing. In addition, the oscillator switching circuits are designed to reduce the noise radiated from the clock driver.