Introduction to 8085 Microprocessor

Names: Kunj Desai (140950107022) Harsh Bajaj (140950107008) Khusboo Jethwa (140950107028)

Branch: CSE A (Batch 1)Semester: 5th Year: 2016

Introduction to 8085 Microprocessor

• Microprocessor is a electronic chip, that functions as the central processing unit of a computer.

• For example: Washing machines, microwave ovens, mobile phones etc.

• Its advance applications are Radar, Satellites, flights.

• All processors are use the basic concept of stored program execution. program or instructions are stored sequentially in the memory. Every microprocessor has its own associated set of instructions. Instruction set for microprocessor is in two forms one in mnemonic, which is comparatively easy to understand and the other is binary machine code.

Diagram of an Intel Microprocessor

Introduction to Intel 8085 Microprocessor

• The Intel 8085 ("eighty-eighty-five") is an 8-bit microprocessor introduced by Intel in 1977.

• The 8085 is a conventional von Neumann design based on the Intel 8080. It is designed by using nmos technology. The "5" in the model number came from the fact that the 8085 requires only a +5-Volt (V) power supply. rather than requiring the +5 V, −5 V and +12 V supplies the 8080 needed. It has 8 bit data bus and 16 bit address bus. it can work up to 5 MHz frequency. It has 40 pins in its chip. Lower order address bus is multiplexed with data bus to minimize the chip size.

Introduction to Intel Microprocessor

• The 8085 has extensions to support new interrupts, with three maskable interrupts (RST 7.5, RST 6.5 and RST 5.5), one non-maskable interrupt (TRAP), and one externally serviced interrupt (INTR). The RST n.5 interrupts refer to actual pins on the processor, a feature which permitted simple systems to avoid the cost of a separate interrupt controller.

Basic features of 8085• 8085 is single chip 8-bit microprocessor.• 8085 microprocessor provides on chip clock

generator.•  One accumulator, one flag register, 6 General

Purpose registers and 2 special purpose register.

• 8-bit ALU.(Arithmetic logical Unit)• 8-bit internal data bus.• 8-bit accumulator.• 16-bit program counter. • 16-bit stack pointer.

Basic features of 8085• Requires a single +5V DC power supply.• 16 address lines, it can access 64K bytes of

memory.• It can run at a maximum frequency of 3 MHz.

Architecture of 8085

Basic Components in 8085Register Section

ALU Section

Interrupt Control Section

Instruction register, Decoder and Control Section

Address and Address/Data buffer

Serial I/O control section

Register Section• Temporary register:(W& Z register)• General purpose register:(B,C,D,E,H&L register)• Special purpose register1. Stack Pointer2. Instruction Register3. Program counter4. Accumulator5. Flag Register

ALU Section• Size: 8-bit• Function: ALU performs the arithmetic

operations and logical operation. Like addition subtraction multiplication division and ANDing, ORing, Ex-ORing

Instruction register, Decoder and Control section

• Instruction registers(IR):-It is a 8-bit register. When an instruction is fetched from memory then it is stored in this register.

• Instruction Decoder:- Instruction decoder identifies the instructions. It takes the information's from instruction register and decodes the instruction to be performed.

• Timing and Control Unit:-It provides timing and control signal to the microprocessor to perform the various operation

Interrupt control section• There are 6 interrupt pins in this unit.• Generally an external hardware is connected to

these pins. These pins provide interrupt signal sent by external hardware to microprocessor and microprocessor sends acknowledgement for receiving the interrupt signal.

• Generally INTA is used for acknowledgement

Address and Address/Data Buffer

Address Buffer:• It is 8-bit unidirectional buffer, Used For address

line• It is used to isolating the microprocessor from

getting loaded.• It used to drive the higher order bus.Address/Data Buffer:• it is 8-bit bidirectional buffer, Used For address line.• It is used to drive the lower order address and data

bus

Serial I/O control section• There are two pins in this unit. 1. SID( serial in data)2. SOD(serial out data)• This unit is used for serial data

communication.1. SID: it is used to receive the data serially.2. SOD: it is used to send the data serially.• The data on these line is accepted or

transferred under software control by serial I/O control block.