Standard features and Pin diagram of AT89C51

· 4K bytes of Flash

· 128 bytes of RAM

· 32 I/O lines (P1, P2, P3, P4)

· 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.