The AT89S2051/S4051 is a low-voltage, high-performance CMOS 8-bit microcontroller with 2K/4K bytes of In-System Programmable (ISP) Flash program memory. The device is manufactured using Atmel's high-density nonvolatile memory technology and is compatible with the industry-standard MCS-51 instruction set. By combining a versatile 8-bit CPU with Flash on a monolithic chip, the Atmel AT89S2051/S4051 is a powerful microcontroller which provides a highly-flexible and cost-effective solution to many embedded control applications. Moreover, the AT89S2051/S4051 is designed to be function compatible with the AT89C2051/C4051 devices, respectively.