MICROPROCESSOR AND INTERFACING

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MICROPROCESSOR AND INTERFACING

• AUTHORS RAMESH.S.GAONKAR
• BADRI RAM
• DOUGLAS.V.HALL
• LIU AND GIBSON

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Syllabus of Microprocessor

• Introduction to microprocessor
• Architecture and block diagram of microprocessor
• 8085 microprocesso
• 8237 DMA Controller
• 8255 Programmable peripheral interface device
• 8254 programmable interval timer
• 8259 programmable inttrupt controller
• 8086 microprocessor

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What is Microprocessor?

• A silicon chip that contains a CPU. In the world
  of personal computers, the terms microprocessor
  and CPU are used interchangeably. At the heart of
  all personal computers and most workstations sits
  a microprocessor. Microprocessors also control
  the logic of almost all digital devices, from
  clock radios to fuel-injection systems for
  automobiles

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Microprocessor def.. Con..

• Microprocessor is a programmable device
• It can be instructed to perform given tasks with
  in its capability.
• The programmer selects instruction from the list
  and determines the sequence of execution for a
  given task.
• It takes input from the input device and process
  the input as it behaves like a CPU and gives the
  output.

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Microprocessor def.. Con..

• Microprocessor is a clock driven semiconductor
  device consisting of electronic logic circuits
  manufactured by using a LSI or VLSI technique.
• Microprocessor can be divided into three segments
• 1)ALU
• 2)Register array
• 3)Control unit

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Block diagram of microprocessor
OUTPUT
Microprocessor As CPU
INPUT
MEMORY
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Characterstics which differentiate microprocessors

• Instruction set The set of instructions that the
  microprocessor can execute.
• bandwidth The number of bits processed in a
  single instruction.
• clock speed Given in megahertz (MHz), the clock
  speed determines how many instructions per second
  the processor can execute.

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Structure of microprocessor

• Chip containing no. of elements for the
  processing purposes.

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History of microprocessor

• Intel's 4004 is considered the first
  microprocesor .
• The 4004 was later followed in 1972 by the 8008,
  the world's first 8-bit microprocessor.

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History of microprocessor

• then is the 8080 microprocessor evolved in 1974.
• Then comes 8085 that is the 8 bit microprocessor

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Continued

• Often the processor is required to manage various
  different tasks that have to be scheduled somehow
  and must also deal with outside interrupt sources
  such as an alarm when something goes wrong.
• Real-time systems are those in which timeliness
  is as important as the correctness of the
  outputs, although this does NOT mean that they
  have to be ?fast systems?.
• A real-time system does not have to process data
  in microseconds to be considered real-time - it
  must simply have response times that are
  constrained and thus predictable.

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Real life applications of microprocessor

• Microprocessors are used to handle a set of tasks
  that control one or more external events or
  systems.
• Microprocessors are typically used in either
  reactive or embedded systems.
• Reactive systems are those that have an ongoing
  interaction with their environment - for example,
  a fire-control system that constantly reacts to
  buttons pressed by a pilot.
• Embedded systems are those used to control
  specialized hardware in which the computer system
  is installed - for example, the microprocessor
  system used to control the fuel/air mixture in
  the carburetor of many automobiles.
•  In embedded systems the software system is
  completely encapsulated by the hardware that it
  controls.

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Some questions

• What is SSI,MSI and LSI?
• What is difference between microprocessor,
  microcontroller and microcomputer?
• What is a bit, byte, nibble and a word?
• What is difference between compiler and
  interpreter?
• What is instruction and mnemonic?

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8085 programming model

• Program counter
• Stack pointer
• General purpose registers
• Accumulator
• Flag registers
• Data and address buses

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8085 instruction set

• Data transfer operations
• Arithmetic operations
• Logical operations
• Branch operations
• Machine control operations

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Data transfer operations

• MOV Rd,Rs
• MVI R,8 bit
• HLT
• IN 8 bit port address accept the data from
  the input port specified in the second byte and
  loads into the accumulator.
• NOP
• OUT 8 bit port address copies the contents of
  the accumulator to the output port specified in
  the second byte,2 byte instruction

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Data transfer operations

• This group of instructions copies data from a
  location called a source to another a location
  called destination without modifying the contents
  of the source.
• Data transfer can be between 1)registers
• Specified data byte to a register or memory
  location
• Between a memory location and a register

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Addressing mode

• Immediate addressing mvi
• Register addressing mov
• Direct addressing in/out ports
• Indirect addressing

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Logical operations

• ANA R
• ANI 8 bit
• ORA R
• ORI 8 bit
• XRA R
• XRI 8 bit
• CMA

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Arthimetic operations

• ADD R
• ADI 8 bit
• SUB R
• SUI 8 bit
• INR R
• DCR R

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Branch operations

• JMP 16 bit 2nd(low) and 3rd(high) byte
  specifies 16 bit
• Memory address
• JC
• JNC
• JZ
• JNZ
• JP
• JM

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Microprocessor architecture

• The process of data manipulation and
  communication is determined by the logic design
  of the microprocessor called the arcitecture.

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Microprocessor architecture

• Microprocessor initiated operations
• Internal operations
• Externally initiated operations
• To perform these functions microprocessor
  requires a group of logic circuits and set of
  signals called control signals.

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Microprocessor initiated operations

• Memory read
• Memory write
• I/O read
• I/O write

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Internal operations

• Store 8-bit data
• Perform arthimetic and logical operations
• Test for conditions
• Sequence the excuetion of operations
• Store data temporarily during excuetion

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8085 pin diagram

• Is 8 bit microprocessor, capable of addressing
  64k of memory
• Has 40 pins ,operate with 3mhz single phase clock
• Require 5v of single power supply

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8085 pin diagram
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8085 pin diagram

• Is 8 bit microprocessor, capable of addressing
  64k of memory
• Has 40 pins ,operate with 3mhz single phase clock
• Require 5v of single power supply

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Pin diagram conti.

• All the signals are classified into 6 groups
• Address bus
• Data bus
• Control and status signals
• Power supply and frequency signals
• Externally initiated signals
• Serial input output ports

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Block diagram of 8085 microprocessor

• It includes
• Arithmetic and logic unit
• Timing and control unit
• Instruction register and decoder
• Register array
• Interrupt control
• Serial input output control

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8085 interrupt

• What is interrupt?
• Vectored interrupt
• Non vectored interrupt
• Enable and disable interrupt instructions
• Pending interrupts

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8085 interrupt

• Interrupt is a process where an external device
  can get the attention of the microprocessor.
• The process starts from the I/O device
• The process is asynchronous.
• Classification of Interrupts
• Interrupts can be classified into two types
• Maskable Interrupts (Can be delayed or Rejected)
• Non-Maskable Interrupts (Can not be delayed or
  Rejected)
• Interrupts can also be classified into
• Vectored (the address of the service routine is
  hard-wired)
• Non-vectored (the address of the service routine
  needs to be supplied externally by the device)

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Interrupts

• An interrupt is considered to be an emergency
  signal that may be serviced.
• The Microprocessor may respond to it as soon as
  possible.
• What happens when MP is interrupted ?
• When the Microprocessor receives an interrupt
  signal, it suspends the currently executing
  program and jumps to an Interrupt Service Routine
  (ISR) to respond to the incoming interrupt.
• Each interrupt will most probably have its own
  ISR.

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Interrupts

• When a device interrupts, it actually wants the
  MP to give a service which is equivalent to
  asking the MP to call a subroutine. This
  subroutine is called ISR (Interrupt Service
  Routine)
• The EI instruction is a one byte instruction
  and is used to Enable the non-maskable
  interrupts.
• The DI instruction is a one byte instruction
  and is used to Disable the non-maskable
  interrupts.
• The 8085 has a single Non-Maskable interrupt.
• The non-maskable interrupt is not affected by the
  value of the Interrupt Enable flip flop.

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8085 intrrupts

• TRAP
• RST7.5
• RST6.5
• RST 5.5
• INTR
• INTA

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Interrupt Vectors and the Vector Table

• An interrupt vector is a pointer to where the ISR
  is stored in memory.
• All interrupts (vectored or otherwise) are mapped
  onto a memory area called the Interrupt Vector
  Table (IVT).
• The IVT is usually located in memory page 00
  (0000H - 00FFH).
• The purpose of the IVT is to hold the vectors
  that redirect the microprocessor to the right
  place when an interrupt arrives.

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• GENERAL PURPOSE PROGRAMMABLE PERIPHERAL DEVICES

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• 8255A Programmable peripheral interface
• 8254 programmable interval timer
• 8259 Programmable interval timer
• 8237 DMA Controller

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8255 Programmable peripheral interface

• It can be programmed to transfer data under
  various conditions.
• It has 24 I/O pins.
• The function of 8255A classified acc to two
  modes.
• A) BSR mode
• I/O mode

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8255 Programmable peripheral interface

• Block diagram of 8255A
• Control word
• BSR mode
• Mode 0
• Mode 1
• Mode 2

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• Control Word
• D7 D6 D5 D4 D3 D2 D1 D0
• 0/1
• BSR Mode I/O Mode
• For port C Mode0 Mode 1
  Mode2
• No effect on mode Simple I/O Handshake
  I/O
• 
  for ports for ports A and or
  B
• 
  A,B,C
• Port C bits

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8254 Programmable interval timer
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8237 DMA Controller

• DMA is an input output technique used for high
  speed data transfer
• Data transfer between system memory and floppy
  disk
• It introduces two new signals that are
• HOLD
• HLDA

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DMA Controller cont.

• DMA Controller consists of
• DMA channels and interfacing
• DMA Signals
• System interface
• Programming the 8237
• DMA Execution consists of
• Master and slave mode

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8086 microprocessor

• It is 16 bit microprocessor.
• Contains 29000 transistors and is fabricated
  using HMOS technology.
• Has addressing capacity of I megabyte.
• Has 20 address pins.
• 5v supply voltage

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8086 Arcitecture

• Internal registers
• Control logic
• Instruction queue
• ALU
• PSW
• Pointers
• Segment registers

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8086 pin diagram
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8086 effective address computations

• To provide flexible base addressing and indexing
  a data address may be formed by addressing
  together a combination of the BX or BP register
  contents SI or DI contents and a displacement.The
  result of such and address computation is called
  effective address.

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8086 memory segmentation

• Address within segments
• Overlapping segments

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Program relocation using CS register

• If a programmer wants to relocate the program by
  any means ,he can relocate the program using cs
  register.

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