Architecture of 8085 Microprocessor V. Mahalakshmi

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Architecture of 8085 Microprocessor


TTS 3061

1154EC106- Basics of Embedded System

Features of 8085 Microprocessor

  • 8 bit general purpose microprocessor.
  • It has 40 pins (dip) dual in line package.
  • Capable of addressing 64K of memory.
  • It requires+5V power supply.
  • It can operate with 3Mhz clock.
  • It provides 74 instructions.
  • It has on chip clock generator.
  • 8-bit data bus.
  • 16-bit address bus, which can address upto 64KB.
  • A 16-bit program counter, stack pointer.

Pin Diagram

Architecture of 8085

Intel 8085 Microprocessor

Microprocessor consists of:

  • Control unit: control microprocessor operations.
  • ALU: performs data processing function.
  • Registers: provide storage internal to CPU.
  • Interrupts
  • Internal data bus, Address bus

Register sets of 8085

General Purpose Registers

  • B, C, D, E, H & L (8 bit regs)
  • Can be used singly or can be used as 16 bit register pairs BC, DE, HL.
  • H & L can be used as a data pointer (holds memory address)
  • Special Purpose Registers
  • Accumulator (8 bit register)



  • It is a 8-bit register which is used to perform arithmetical and logical operation.
  • It stores the output of any operation.
  • It also works as registers for i/o accesses.
  • Temporary Register

  • It is a 8-bit register which is used to hold the data on which the accumulator is computing operation.
  • It is also called as operand register because it provides operands to ALU.

Control signals of 8085

  • Arithmetic Latch Enable (ALE)
  • It is an output signal used to give information of AD0-AD7 contents. High – Address, Low - Data

    2.Read (RD) signal

    This is active low used for reading operation.

    3.Write signal (WR)

    This is active low used for writing operation.

Status signals

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