8085 microprocessor PPT and PDF Report: Central Processing Unit (CPU) is carved on a single chip is called a microprocessor. The functional components of a CPU are Arithmetic Logic Unit (ALU), Control and Timing Units, registers are found in a single integrated circuit called IC. The INTEL 8085 microprocessor is a second generation microprocessor and is an eight-bit processor designed in the year of 1976 with the NMOS technology with a 40 pin DIP, approximately consisting 6500 transistors having a power supply of 5V.

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8085 microprocessor PPT and PDF Report


The 40 pins of a microprocessor are classified as follows:

  1. 1 (read operation) (Write operation): A low on   states an opinion that the These lines or signals are most importantly used for checking the directions of data flow data must be read from the chosen memory location over the data bus. A low on   states an opinion that the data must be written in the chosen memory location over a data bus. 
  2. Address Latch Enable (ALE): AD0 to AD7 lines are multiplexed with the lower half of the 16-bit address (AD0 – AD7) and this appears only at the foremost part of the machine cycle (T1). But this address is also required during remaining parts of the cycle (T2 and T3) to approach a specific location in memory or input/output port. So, the lower half of an address need to be latched in “T1” to make it available at T2 and T3. This can be done through an external latch and ALE signal from 8085.
  3. Control and Status Lines:
  • Address Bus: The 16-bit address upper half appears on the address bus or address lines (A8 – A15). These lines are only used for the most important eight bits of the 16-bit address.
  • Data Bus: The eight-bit data bus (D0 – D7) is multiplexed with the 16 bit’s lower half address bus (A0 – A7).
  •  I0/, S0, and S1: The signal I0/ states an opinion that whether input/ output operation or memory operation is being done, whereas S0 and S1tells the about the machine cycle in progress.
  • READY: This signal is used by the microprocessor to know whether a peripheral is set or not to send the data. If it is not ready the processor waits and is used to make the slower peripherals of microprocessor agree or occur in time.

4. Interrupt Signals: The 8085 has five hardware interrupts or externally initiated signals and they are: RST 5.5,  RST 6.5, RST 7.5, TRAP and INTR (interrupt), show that the processor has an interrupt.

5.  Serial Data Transfer: SID and SOD are used to accept and transmit the data in bit by bit format.

6.  DMA Controllers: HOLD and HLDA are the two DMA signals.

7.  Reset Signals: The two reset signals are RESET IN and RESET OUT.

8.  Power Supply and Clock: It requires a power supply of 5V and CLK OUT is used as a system clock.


  1. Arithmetic Logic Unit (ALU): Arithmetic logic unit carries out bitwise arithmetic operations such as addition, subtraction. It also carries out the logical operations like AND, OR rotate and much more.
  2. Timing and Control Unit: The control unit is obliged for all operations and the operations occur at the same time with the help of clock signal.
  3. General Purpose Registers: The eight-bit general purpose registers are B, C, D, E, H, L and these can be used as single eight-bit registers and in pairs as 16-bit registers like BC, DE etc., these are also called as scratch pad registers.
  4. Program Status Word: The group of five flip-flops which deed as status flags and in INTEL 8085 the five status flags are: Carry (CS), Zero (Z), Sign (S), Parity (P), and Auxillary Carry (AC) and along with these there are three undefined bits which together called as program status word.
  5. Program Counter: Program is a collection of instructions and microprocessor searches these instructions from memory. Well, a program counter is a unique register which saves the address of next instruction to be searched.
  6. Stack Pointer: Stack is a reticent part of the memory in RAM where temporary data can be saved.
  7. Instruction Register and Decoder: The processor foremost searches the op-code instruction from the memory and it is stored in a register called instruction register. The stored instruction is sent to the instruction decoder where it is decoded and according to it, the timing and control signals are generated.
  8. Interrupt Control: Normally the processor executes the operations in an order but sometimes it need to automatically execute a collection. After such execution, the program counter needs to come back in the normal condition and the occurrence of such special condition is called interrupt.
  9. Serial I/O Control: This provides two signals namely SID and SOD which are used to receive and transmit the information serially.
  10. Address and Data Bus: 8085 microprocessor’s data bus is eight bit long and eight bits of information can be transmitted over it. In a case of 16 bits of information, the most important bits of an address are sent through (A8 TO A15) and the remaining bits are sent through AD0 to AD7.


The 8085 microprocessor has seven basic machine cycles. They are:

  1. Op-code fetches cycle: Used in executing the operations and it requires 4T OR 6T states.
  2. Memory Read Cycle: Availed to search one byte of memory and 3T- states are needed.
  3. Memory Write Cycle: Availed to send one byte of memory and 3T- states are needed.
  4. I/O Read Cycle: Availed to search one byte of memory from I/O port and 3T- states are needed.
  5. I/O Write Cycle: Availed to write one byte of memory from I/O port and 3T- states are needed.
  6. Interrupt Acknowledge Cycle: The address of interrupt service is needed for the service of the interrupted machine. It requires 6T or 12T states.
  7. Bus idle cycle: Data bus of a microprocessor is not availed.

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Content of the Seminar and pdf report for 8085 microprocessor

  • Introduction
  • Features
  • Pin Configuration
  • Architecture 0f 8085
  • The 8085 Bus Structure
  • Instruction Set
  • Addressing Modes
  • Timing diagrams
  • Reference

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