Q.How many serial ports are there in 8051?

The 8051 is the classic 8-bit microcontroller studied in II PUC Electronics, and its architecture is a favourite board-exam topic. On a single chip it brings together all the blocks a small computer needs: an ALU, an 8-bit CPU with the working registers A (accumulator) and B, internal program memory, internal data memory, I/O ports, timers, a serial port, and interrupt and clock circuits.

Its headline feature quantities are worth memorising: 4 KB of on-chip ROM for the fixed program, 128 bytes of internal RAM for data, two 16-bit timer/counters (T0 and T1), one serial port, 32 I/O pins arranged as four 8-bit ports (P0-P3), and six interrupt sources (two external, three internal, plus serial). It uses a 16-bit Program Counter, giving access to a 64 KB program space, and follows a CISC (Complex Instruction Set Computer) design. …