The AT89C4051 provides the following standard features: 4K bytes of Flash,128 bytes of RAM, 15 I/O lines, two 16-bit timer/counters, a five-vector, two-level inter-rupt architecture, a full duplex serial port, a precision analog comparator, on-chip oscillator and clock circuitry. In addition, the AT89C4051 is designed with static logic for operation down to zero frequency and supports two software-selectable power saving modes. The Idle Mode stops the CPU while allowing the RAM,timer/counters,serial port and interrupt system to continue functioning. The power-down mode saves the RAM contents but freezes the oscillator disabling all other chip functions until the next hardware reset.