The AT89S51-24PU is a low-power, high-performance CMOS 8-bit Microcontroller, uses Atmel's high-density non-volatile memory technology and is compatible with the industry-standard 80C51 instruction set and pin-out. The on-chip Flash allows the program memory to be reprogrammed in-system or by a conventional non-volatile memory programmer. By combining a versatile 8-bit CPU with in-system programmable flash on a monolithic chip, the Atmel AT89S51-24PU is a powerful microcontroller which provides a highly-flexible. It provides the following standard features 32 I/O lines, Watchdog timer, two data pointers, two 16-bit timer/counters, a five-vector two-level interrupt architecture, a full duplex serial port, on-chip oscillator and clock circuitry. In addition, the microcontroller is designed with static logic for operation down to zero frequency and supports two software selectable power saving modes.