Describe the basic architecture of the 8051 microcontroller.

The 8051 is an 8-bit microcontroller with: 4KB internal ROM (program memory), 128 bytes internal RAM (data memory), Four 8-bit I/O ports (P0-P3), Two 16-bit timers/counters, Full-duplex UART serial port, On-chip oscillator, Five interrupt sources with two priority levels. It uses Harvard architecture with separate program and data memory spaces. The CPU has an accumulator, B register, PSW (program status word), and four register banks. External memory can be expanded to 64KB each for code and data.