8085 Microprocessor Architecture & Working

Generally, the 8085 is an 8-bit microprocessor, and it was launched by Intel team in the year of 1976 with the help of NMOS technology. This processor is the updated version of the microprocessor. The configurations of 8085 microprocessor mainly include data bus-8-bit, address bus-16 bit, program counter-16-bit, stack pointer-16 bit, registers 8-bit, +5V voltage supply and works at 3.2 MHz single segment CLK. The applications of 8085 microprocessor include microwave ovens, washing machines, gadgets, etc. This article discusses an overview of what is 8085 microprocessor architecture.

8085 Microprocessor Architecture

The architecture of 8085 microprocessor mainly includes the timing & control unit, Arithmetic and logic unit, decoder, instruction register, interrupt control, a register array, serial input/output control. The most important part of the microprocessor is the central processing unit.

8085 Architecture
                                                                       8085 Architecture

Operations of 8085 Microprocessor

The main operation of ALU is arithmetic as well as logical which includes addition, increment, subtraction, decrement, logical operations like AND, OR, Ex-OR, complement, evaluation, left shift or right shift. Both the temporary registers as well as accumulators are utilized for holding the information throughout in the operations then the outcome will be stored within the accumulator. The different flags are arranged or rearrange based on the outcome of the operation.

Flag Registers

The flag registers of microprocessor 8085 are classified into five types namely sign, zero, auxiliary carry, parity and carry. The positions of bit set aside for these types of flags. After the operation of an ALU, when the result of the most significant bit (D7) is one, then the sign flag will be arranged. When the operation of the ALU outcome is zero then the zero flags will be set. When the outcome is not zero then the zero flags will be reset.

In an arithmetic process, whenever a carry is produced with the lesser nibble, then an auxiliary type carry flag will be set. After an ALU operation, when the outcome has an even number then the parity flag will be set, or else it is reset. When an arithmetic process outcome in a carry, then carry flag will be set or else it will be reset. Between the five types of flags, the AC type flag is employed on the inside intended for BCD arithmetic as well as remaining four flags are used with the developer to make sure the conditions of the outcome of a process.

Control and Timing Unit

The control and timing unit coordinates with all the actions of the microprocessor by the clock and gives the control signals which are required for communication among the microprocessor as well as peripherals.


Decoder and Instruction Register
As an order is obtained from memory after that it is located in the instruction register, and encoded & decoded into different device cycles.

Register Array

The general purpose programmable registers are classified into several types apart from the accumulator such as B, C, D, E, H, & L. These are utilized as 8-bit registers otherwise coupled to stock up the l6 bit of data. The permitted couples are BC, DE & HL, and the short term W & Z registers are used in the processor & it cannot be utilized with the developer.

Special Purpose Registers

These registers are classified into four types namely program counter, stack pointer, increment or decrement register, address buffer or data buffer.

Program Counter

This is the first type of special purpose register and considers that the instruction is being performed by the microprocessor. When the ALU completed performing the instruction, then the microprocessor searches for other instruction to be performed. Thus, there will be a requirement of holding the next instruction address to be performed in order to conserve time. Microprocessor increases the program when an instruction is being performed, therefore that the program counter position to the next instruction memory address is going to be performed…

Stack Pointer in 8085

The SP or stack pointer is a 16-bit register and functions similar to a stack, which is constantly increased or decreased with two throughout push and pop processes.

Increment or Decrement Register

The 8-bit register contents or else a memory position can be increased or decreased with one. The 16-bit register is useful for incrementing or decrementing program counters as well as stack pointer register content with one. This operation can be performed on any memory position or any kind of register.

Address-Buffer & Address-Data-Buffer

Address buffer stores the copied information from the memory for the execution. The memory & I/O chips are associated with these buses; then the CPU can replace the preferred data by I/O chips and the memory.

Address Bus and Data Bus

The data bus is useful in carrying the related information that is to be stock up. It is bi-directional, but address bus indicates the position as to where it must be stored & it is uni-directional, useful for transmitting the information as well as address input/output devices.

Timing & Control Unit

The timing & control unit can be used to supply the signal to the 8085 microprocessor for achieving the particular processes. The timing and control units are used to control the internal as well as external circuits. These are classified into four types namely control units like RD’ ALE, READY, WR’, status units like S0, S1, and IO/M’, DM like HLDA, and HOLD unit, RESET units like RST-IN and RST-OUT.

8085 Microprocessor Instruction Set

The instruction set of 8085 microprocessor is nothing but instruction codes used to achieve an exact task, and instruction sets are categorized into various types namely control, logical, branching, arithmetic, and data transfer instructions.

Addressing Modes of 8085

The addressing modes of 8085 microprocessor can be defined as the commands offered by these modes which are utilized for denoting the information in different forms without altering the content. These classified into five groups namely immediate, register, direct, indirect and implied addressing mode.

Thus, this is all about 8085 architecture. From the above information finally, we can conclude that 8085 microprocessor features are it is an 8-bit microprocessor, enclosed with 40-pins, uses +5V supply voltage for the operation. It consists of the 16-bit stack pointer and program counter, and 74-instruction sets, and many more. Here is a question for you, what are the applications of 8085 microprocessor?

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