ATMEL AT89S52 is a 8051 compatible 8 bit microcontroller, comes in  40 Pin DIP package. It has  8K bytes of In-System Programmable (ISP) Flash memory. It has 4 general purpose ports (32 I/O lines) from which port 0  is open drain out put for driving high current devices. This chip has Three-Level Program Memory Lock, 3 Timers/Counters, 8 Interrupts Sources, Watchdog Timer, 256 Bytes On-chip RAM.