Working of 8085based Single board microcomputer (original) (raw)

Last Updated : 21 Apr, 2026

A single board microcomputer uses a monitor program (stored in ROM/EPROM starting at address 0000H) to control system operations. When the system is powered on or reset, the program counter is cleared to 0000H, and the MPU begins executing the monitor program.

• The monitor program performs key functions such as scanning the keyboard, displaying input (e.g., on LEDs), storing data in memory, and transferring control to the user program when the Execute key is pressed.
• The user enters a program into R/W memory using the keyboard. After entry, pressing the Run/Execute key transfers control to the user program.
• The MPU then fetches, decodes, and executes instructions sequentially until a Halt instruction is encountered.

Features

• **8-bit microprocessor: The 8085 microprocessor is an 8-bit processor, which means it can handle 8 bits of data at a time. This limits its processing power compared to newer processors, but it is still capable of running a wide range of software and applications.
• **Memory: The microcomputer typically includes memory, which is used to store the program instructions and data being processed by the microprocessor. The memory may include both read-only memory (ROM) and random access memory (RAM).
• **I/O ports: The microcomputer typically includes a variety of I/O ports, such as serial and parallel ports, which are used to interface with other devices.
• **Clock: The microprocessor requires a clock signal to synchronize its operations, and the microcomputer typically includes a clock generator to generate the necessary clock signal.

Advantages

• **Cost-effective: The 8085-based single board microcomputer is a cost-effective solution for many applications, as it provides a complete system on a single board, eliminating the need for additional hardware.
• **Easy to use: The 8085 microprocessor is a well-established architecture that is easy to use and program, making it suitable for a wide range of applications.
• **Availability of software tools: A wide range of software tools and compilers are available for the 8085 microprocessor, which makes it easier to develop and debug applications.
• **Expandability: The single board microcomputer can be expanded with additional peripherals such as I/O devices, memory, and communication interfaces, making it suitable for a variety of applications.
• **Low power consumption: The 8085 microprocessor is a low power device, which makes it suitable for battery-powered applications.

Disadvantages

• **Limited processing power: The 8085 microprocessor has limited processing power compared to more modern microprocessors, which can limit the performance of the system.
• **Limited memory: The 8085 microprocessor has a limited address space, which can limit the amount of memory that can be used in the system.
• **Limited peripherals: The 8085 microprocessor has limited built-in peripherals, which can limit the functionality of the system.
• **Limited connectivity: The 8085 microprocessor has limited connectivity options, which can limit the ability to interface with external devices.
• **Limited availability: The 8085 microprocessor is an older architecture, which may limit its availability and support in the future.