Difference between AT89C51 AT89C52 and AT89C2051

Parameter	AT89C51	AT89C52	AT89C2051
Flash Memory Size	4K Bytes of In-System Reprogrammable Flash Memory	8K Bytes of In-System Reprogrammable Flash Memory	2K Bytes of Reprogrammable Flash Memory
Endurance	1,000 Write/Erase Cycles	1,000 Write/Erase Cycles	10,000 Write/Erase Cycles
Data Memory Size	128 X 8 bit internal RAM	256 X 8 bit internal RAM	128 x 8-bit Internal RAM
Operating Voltage	5V (up to 6.6V)	5V (up to 6.6V)	2.7V to 6V
Programmable I/O Lines	32	32	15
Timers/Counters	Two 16 bit	Three 16 Bit	Two 16 bit
Interrupt Sources	Six	Eight	Six