Pin Diagram of 8051 Microcontroller | PIN Configurations of 8051 | 8051 Microcontroller

Summary

This video lecture series on the 8051 microcontroller focuses on the pin diagram, explaining its crucial role in understanding the microcontroller's functions. The instructor details the power supply pins, clock terminals, reset function, and the significance of the ALE and EA signals for memory interfacing. The video also covers the multiple functionalities of the 8051's ports, including their use in I/O operations, address/data lines, and timer inputs, emphasizing the microcontroller's efficiency in utilizing its 40 pins.

Takeaways

• 🔋 The 8051 microcontroller is powered by two pins, VCC and VSS, with VCC receiving 5V and VSS being the ground reference.
• 🕰️ The 8051 uses two pins, XTAL1 and XTAL2, for the crystal clock, typically operating at 12 MHz for general use and 11.0592 MHz for serial communication at universal baud rates like 9600.
• 🔄 The reset terminal is used to reset the 8051, setting the program counter to the reset vector address 0000h, allowing the execution of BIOS programs to set up the system.
• 📏 The ALE (Address Latch Enable) signal is crucial for interfacing external memory, distinguishing between address and data on the data bus AD0 to AD7.
• 🛡️ The EA/VPP pin determines the use of the internal 4KB ROM; setting it to 0 discards the internal ROM, while setting it to 1 enables it, with external ROM interfacing starting from 1000h if EA/VPP is 0.
• 📚 The PSEN (Program Store Enable) terminal is used for reading data from external ROM, distinguishing it from RAM read/write operations which use separate signals.
• 🔢 The 8051 has 4 bit-addressable ports (Port 0, 1, 2, and 3), each with 8 pins, offering various functionalities including I/O operations and multiplexing for address/data lines.
• 🔣 Port 0 has multiple functionalities including acting as an I/O port, byte operation, and as address/data multiplexed lines, controlled by the ALE signal.
• 🔄 Port 1 serves as a standard I/O port with byte and bit operations but lacks the multiple functionalities of Port 0.
• 🔗 Port 2 is bit and byte addressable and can also provide upper address bits (A8 to A15) for external memory interfacing.
• 🛑 Port 3 is bit and byte addressable with multiple alternate functions including serial communication (RxD and TxD), interrupts (INT0 and INT1), and timer inputs (T0 and T1), along with control signals for external RAM access (RD and WR).

Q & A

What are the two pins used to power up the 8051 microcontroller?

The two pins used to power up the 8051 microcontroller are VCC and VSS, where VCC is provided with a 5-volt supply and VSS is connected to the ground reference.

What is the purpose of the external crystal clock in the 8051 microcontroller?

The external crystal clock, such as the 12 megahertz crystal mentioned in the script, is used to provide a stable clock signal for the microcontroller's operation.

Why is a crystal frequency of 11.592 megahertz used for serial communication in the 8051?

A crystal frequency of 11.592 megahertz is used for serial communication to operate at universal baud rates, such as 9600 baud rate, which is a standard for UART and many serial communication techniques.

What happens when the reset terminal of the 8051 microcontroller is activated?

When the reset terminal of the 8051 microcontroller is activated, the program counter becomes 0000h, also known as the reset vector address, and the microcontroller starts executing BIOS programs to set up the system.

What is the function of the ALE (Address Latch Enable) signal in the 8051 microcontroller?

The ALE signal is used to separate address and data on the data bus of the 8051 microcontroller. When ALE is high, the bus carries addresses, and when it is low, the bus carries data.

What is the significance of the EA (External Access) pin in the 8051 microcontroller?

The EA pin determines whether the 8051 microcontroller uses its internal ROM or an external ROM. When EA is set to 0, the internal ROM is discarded, and when it is set to 1, the internal 4KB ROM is used.

What is the role of the PSEN (Program Store Enable) pin in accessing external ROM?

The PSEN pin is used to read data from an external ROM. It is essential for accessing program data stored in external ROM when the 8051 microcontroller has both internal and external memory interfaces.

How many ports does the 8051 microcontroller have, and what are their names?

The 8051 microcontroller has four ports: Port 0, Port 1, Port 2, and Port 3. Each port is bit-addressable and can be used for various functions, including I/O operations.

What are the multiple functionalities of Port 0 in the 8051 microcontroller?

Port 0 has multiple functionalities, including working as an I/O port, byte operation, 1-bit operation, and also serving as an address/data multiplexed line with the help of the ALE signal.

What are the alternate functions of Port 3 in the 8051 microcontroller?

Port 3 has alternate functions such as serial communication with pins P3.0 (RxD) and P3.1 (TxD), hardware interrupts with pins P3.2 and P3.3, and timer inputs with pins P3.4 (T0) and P3.5 (T1). Additionally, it includes read and write enable signals for external RAM with P3.6 (RD) and P3.7 (WR).