What is the difference between 8051 and 8052 microcontrollers?

8051 and 8052 aren't interchangable, but they are similar.

The 8052 is identical to the 8051 with the following enhancements:

1. The 8052 has 256 bytes of internal RAM, the 8051 has 128.

2. The 8052 has three (3) 16-bit timers, the 8051 has two (2). The third timer has some new operation modes not available with the 8051.