Microcontroller having _____ pins used for parallel I/O.

Question

Examoogle · Accepted Answer

32

Explanation: The standard 8051 microcontroller is equipped with 4 parallel I/O ports (P0, P1, P2, and P3), each containing 8 pins. Since $4 	imes 8 = 32$, the microcontroller provides 32 pins dedicated to parallel input/output operations.

Working Principle: Each port (P0 to P3) acts as an 8-bit bidirectional data bus. Port 0 is typically used as a multiplexed address/data bus, while Ports 1, 2, and 3 serve as general-purpose I/O, though some pins in Port 3 have dual functions (interrupts, serial communication, timers). The architecture uses internal latches to hold the state of each pin, allowing the CPU to read from or write to these pins as part of the internal Special Function Register (SFR) memory space.

Key Formulas: $TotalPins = N_{ports} 	imes Bits_{per\_port}$; $TotalPins = 4 	imes 8 = 32$

Key Points: The 8051 has 40 pins in total, including power supply, oscillator, reset, and control signals.; 32 pins out of the 40 are specifically assigned for parallel I/O.; Ports can be configured as input or output by writing to the corresponding port latches.

Advantages: Direct interface with peripheral devices.; Bit-addressable capability allows fine-grained control.

Disadvantages: Limited pin count for complex systems requiring expansion.; Multiplexing on Port 0 and 2 reduces available I/O when using external memory.

Applications: Interfacing LED arrays and Keyboards.; Interfacing LCD displays.; Direct communication with simple digital sensors.

Additional Info: The 8051 package is typically a 40-pin DIP (Dual In-line Package).. The remaining 8 pins are dedicated to VCC, GND, XTAL1, XTAL2, RST, ALE/PROG, PSEN, and EA.

Answer: B is correct — The 8051 microcontroller utilizes 4 ports (P0, P1, P2, P3), each being 8-bits wide, resulting in 32 dedicated I/O pins.

Exam Tip: Always remember that the 40-pin DIP package of the 8051 is divided into 32 I/O pins and 8 system/control pins (Power, Clock, Reset, etc.).

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