AT89C52 – 8 bit Microcontroller  belongs to Atmel’s 8051 families. AT89C52 has 8KB of Flash programmable and erasable read-only memory (PEROM) and 256 bytes of RAM. it has an endurance of 1000 Write/Erase cycles which means that it can be erased and programmed to a maximum of 1000 times. Specifications of Atmel AT89C52 Microcontroller: Pin No Function Name 1 External count input to Timer/Counter 2, clock-out T2 P1.0 2 Timer/Counter 2 capture/reload trigger and direction control T2 EX P1.1 3 8 bit input/output port (P1) pins P1.2 4 P1.3 5 P1.4 6 P1.5 7 P1.6 8 P1.7 9 Reset pin; Active high Reset 10 Input (receiver) for serial communication RxD 8 bit input/output port (P3) pins P3.0 11 Output (transmitter) for serial communication TxD P3.1 12 External interrupt 1 Int0 P3.2 13 External interrupt 2 Int1 P3.3 14 Timer1 external input T0 P3.4 15 Timer2 external input T1 P3.5 16 Write to external data memory Write P3.6 17 Read from external data memory Read P3.7 18 Quartz crystal oscillator (up to 24 MHz) Crystal 2 19 Crystal 1 20 Ground (0V) Ground 21 8 bit input/output port (P2) pins / High-order address bits when interfacing with external memory P2.0/ A8 22 P2.1/ A9 23 P2.2/ A10 24 P2.3/ A11 25 P2.4/ A12 26 P2.5/ A13 27 P2.6/ A14 28 P2.7/ A15 29 Program store enable; Read from external program memory PSEN 30 Address Latch Enable ALE Program pulse input during Flash programming Prog 31 External Access Enable;  Vcc for internal program executions EA Programming enable voltage; 12V (during Flash programming) Vpp 32 8 bit input/output port (P0) pins Low-order address bits when interfacing with external memory P0.7/ AD7 33 P0.6/ AD6 34 P0.5/ AD5 35 P0.4/ AD4 36 P0.3/ AD3 37 P0.2/ AD2 38 P0.1/ AD1 39 P0.0/ AD0 40 Supply voltage; 5V (up to 6.6V) Vcc                                                             Package Includes:  1 x Atmel AT89C52 Microcontroller