Introduction of Microcomputer System (original) (raw)

Last Updated : 21 Apr, 2026

Microcomputer systems are small and inexpensive computers that are widely used in various applications. The 8085 microprocessor is an example of a Microcomputer System. A microprocessor system contains two types of memory that are EPROM and R/WM, Input and Output devices, and the buses that are used to link all the peripherals (memory and I/Os) to the MPU.

The Microprocessor Unit (MPU)

The MPU is the brain of the microcomputer system. It contains the arithmetic and logic unit (ALU) and the control unit (CU) that work together to execute instructions. The 8085 microcomputer system has 16 address lines ranging from A0 to A15 that are used to address memory. The lower-order address bus A0-A7 is used to identify the input and output devices.

Memory

There are two types of memory in the microcomputer system: Erasable Programmable Read-Only Memory (EPROM) and Random-Access Read-Write Memory (R/WM). EPROM is a type of memory that can be programmed once and can be erased by exposing it to ultraviolet light. R/WM is a type of memory that can be both read and written to. The MPU communicates with memory through memory read and memory write control signals.

Input and Output (I/O) Devices

The microcomputer system contains input and output (I/O) devices that allow the system to interact with the external environment. The microcomputer system has 8 data lines, D0-D7, which are bidirectional and common to all devices. The microcomputer system generates four control signals: memory read, memory write, I/O read, and I/O write. These signals are connected to different peripheral devices.

Interfacing Devices

The MPU communicates with one peripheral at a time by placing the device address on the address bus, data on the data bus, and enabling it using control signals (e.g., I/O Write). Only the selected device is active, while others remain in a high-impedance (tri-state) state.

• Interfacing devices are semiconductor components used to connect peripherals to the bus system. 7
• They include decoders (for address selection), bus drivers (to boost signal strength), and latches (to hold data).
• These devices ensure proper communication between the MPU and peripherals in a microcomputer system.

The block diagram of a microcomputer system is shown below:

Advantages

• **Flexibility: A microcomputer system can be customized to meet the needs of a wide range of applications. It can be programmed to handle a variety of tasks, and its components can be easily upgraded or replaced as needed.
• **Cost-effective: Microcomputer systems are generally less expensive than larger computer systems, which makes them a cost-effective solution for many applications.
• **Compact size: Microcomputer systems are typically small and compact, which makes them ideal for applications where space is limited.
• **Ease of use: Microcomputer systems are generally easy to use, particularly for individuals with basic computer skills. They typically come with user-friendly interfaces and software that make them easy to operate.

Disadvantages

• **Limited processing power: Microcomputer systems typically have limited processing power compared to larger computer systems. This can limit their ability to handle complex tasks or run resource-intensive software.
• **Limited memory capacity: Microcomputer systems typically have limited memory capacity compared to larger computer systems. This can limit their ability to handle large amounts of data or run complex software.
• **Limited I/O options: Microcomputer systems typically have limited I/O options compared to larger computer systems. This can limit their ability to interface with other devices or handle complex I/O operations.
• **Limited expansion options: While microcomputer systems can be upgraded or replaced, they typically have limited expansion options compared to larger computer systems. This can limit their ability to grow or adapt to changing needs over time.