microcontroller is a small computer on a single IC that integrates all the features that are found in the microprocessor. In order to serve the different applications, they have a high concentration of on chip facilities such as RAM, ROM, I/O ports, timers, serial port, clock circuit and interrupts. Microcontrollers are used in various automatic controlled devices such as remote controls, automobile engine control systems, medical devices, power tools, office machines, toys, power tools and other embedded systems. Therefore, this article gives an overview of pin diagram of 8051 microcontroller with explanation and 8051 based project ideas.
8051 Microcontroller
In case of microprocessor, we have to interface additional circuitry externally, such as RAM, ROM, I/O ports, timers, serial port, clock circuit, other external peripherals whereas in the microcontroller, all these peripherals are in built. Let us look on in brief about pin diagram of 8051 microcontroller.
Microcontroller Pins Working
8051 microcontrollers have four I/O ports where each port containing 8 pins that can be configured as inputs or outputs. Pin configuration, i.e. whether it is to be configured as an i/p (1) or an o/p (0), depends on its logic state. In order to configure a microcontroller pin as an output, it is necessary to apply a logic zero (0) to suitable I/O port bits. In this case, the voltage level on appropriate pin will be 0.
Similarly, in order to configure a microcontroller pin as an input, it is necessary to apply a logic one (1) to the suitable port. In this case, the voltage level on appropriate pin will be 5V. This may seem confusing, It all becomes clear after studying simple electronic circuits connected to an I/O pin.
Input/Output (I/O) Pin
The below figure shows a simplified schematic of all circuits within the microcontroler which is connected to one of its pins. It states to all the pins except those of the P0 port which do not have pull-up resistors built-in.
Input/Output (I/O) Pin
Output pin
A logic 0 is applied to a bit of the register P then, the output FE transistor is turned on, therefore connecting the appropriate pin to ground.
Output pin
Input pin
A logic 1 is applied to a bit of the P register. The output field effect transistor is turned off and the appropriate pin remains connected to the power supply voltage, over a pull-up resistor of high resistance.
Input Pin
Pin Diagram of 8051 Microcontroller
8051 microcontroller families (89C51, 8751, DS89C4xO, 89C52) come in different packages like quad flat package, leadless chip carrier and dual in line package. These all packages consist of 40 pins which are dedicated to several functions such as I/O, address, RD, WR, data and interrupts. But, some companies offer a 20 pin version of themicrocontrollers for less demanding applications by reducing the number of I/O ports. Nevertheless, since the vast majority of developers use the 40 pin chip.
Pin Diagram of 8051 Microcontroller
The pin diagram of 8051 microcontroller consists of 40 pins and that is shown below. A total of 32 pins are set away into four Ports such as P0, P1, P2 and P3. Where, each port contains 8 pins. Therefore, microcontroller 8051 pin diagram and explanation is given below.
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