The PIC18F4520-I/P is an Enhanced Flash Microcontroller with 10-bit A/D and nanoWatt technology. The PIC18F4520 family introduces design enhancements that make these microcontrollers a logical choice for many high-performance and power sensitive applications. The PIC18F4520 family incorporates a range of features that can significantly reduce power consumption during operation. The PIC18F4520 device include an internal oscillator block which generates two different clock signals, either can be used as the microcontroller's clock source. This may eliminate the need for external oscillator circuits on the OSC1 or OSC2 pins. The PIC18F4520 microcontroller can be serially programmed while in the end application circuit. This is simply done with two lines for clock and data and three other lines for power, ground and the programming voltage.