intriduction ii

8/10/2019 Intriduction II

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KNL3473Microprocessor

Introduction toMicroprocessors(II)


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Memory Read Operation - Step 1

CPU Memory

Address bus

Data bus

CPU places address (XXXX) of thememory location on the address bus

Memory request

Read

The CPU sends out the control signalsMemory

RequestandReadto indicate that it wants to

read from memory


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CPU Memory

Address bus

Data bus

Memory request

Read

Accessed location at XXXX

Memory places data from theaccessed location onto the data bus


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CPU Memory

Address bus

Data bus

Memory request

Read

Memory request

Read

The CPU removes theMemory Request

andRead signals

CPU latches the data into a register

Register


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Memory Write Operation - Step 1

CPU Memory

Address bus

Data bus

CPU places address (YYYY) of thememory location on the address bus

The CPU sends out aMemory Requestcontrol

signal to indicate that it wants to perform a

memory operation

Memory request


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CPU Memory

Address bus

Data bus

Memory request

CPU places the data from a register

onto the data bus

Register

The CPU sends out a Writecontrol signal to

indicate that valid data is available on the data

bus

Write


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CPU Memory

Address bus

Data bus

Memory request

Memory copies the data bus into the

accessed location

Register

Write

Accessed locationat YYYY

The CPU removes the Writesignal to complete

the memory write operation

Memory request

Write


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Microprocessor System Vs Microcontroller System

CPU

General

purpose

Micro

processor

Data Bus

Address Bus

RAM ROM I / OPort

TimerSerial

COM

Port

CPU RAM ROM

I / O

PortTimer

Serial

COM

Port

General-Purpose Microprocessor System Microcontroller


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Microprocessor System Vs Microcontroller System

P C

Hardware

Architecture

Single-chip CPURAM-ROM ratio high

Interrupt, I/O, Timer external.

Not much on Real-time

Single-chip ICROM-RAM ration high

Interrupt, I/O, timer-InternalNeed to respond to Real time

Application Microcomputer systemProcessing information

Control oriented activitiesControl of I/O devices

Instruction

set

Process intensive to handle

Large volume of data

Operates on byte, words,

pointers, and arrays.Longer development time

ANDing, ORing, XORing inbit level is less easy

Control intensive to handle

I/O using single Bit

Operates mostly on Bit & byte

shorter development time

ANDing, ORing, XORing inbit level is easy


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Features 8-bit general-purpose microprocessor capable of addressing

64K of memory.

Intel 8085 microprocessor is the next generation of Intel 8080.8085s processing speed is faster than the 8080.

The device has

1. 40 pins2. Positive 5 V single power supply

3. Operate with a 3-MHz single-phase clock

4. 16 bit address bus

5. 8 bit multiplex data bus

6. Control and status signals

7. Externally initiated signals

8. Serial I/O ports.


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Common Microprocessor Internal

Block Diagram


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Block Diagram

1. Logic functions for data processing.

2. Data handling.

3. How each of these logic functions is

connected to all the others. Referring to a block diagram makes it

easier to see how to use a microprocessor

in hardware and system design situations.

The block diagram makes it easier to

understand the architecture of a

microprocessor.


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Status register word used in 8-bit

Microprocessor

P - Is set to 1 if the result has an even number of 1s.

OIs set to 1 if carry happen between bit 6 and 7 or bit 7 and 8.

IIs set to 1 if a carry happen between bit 3 and 4.

CIs set to 1 if and arithmetic operation results in a carry.

NIs set to 1 if bit 7 of the result =1.

ZIs set to 1 when the result is zero.


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Continue

Sometimes called a flag register. ALU operations set the status registers bits.

The status register stores the results of tests forconditions that are generated by ALU operations.

Data in the status register can be placed on themicroprocessor internal data bus but cannotreceived data from the microprocessor internaldata bus (read only).

Mathematical operations can produce a carry bit,

or they can result in a logic 0 (cleared register), orboth.

If two 8-bit numbers are added, and their sum isgreater than 11111111, then a carry is generated.


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Example

1. If we add 1110 1110 and 0111 0000, we get

1110 1110

+ 0111 0000

We get 1 0101 1110

carry 8-bi t posit ive result

This operation sets the status registers carrybit to log ic 1.


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Example

2. If we add 0001 1111 and 0100 0001

0001 1111

+ 0100 0001

We get 0 0110 0000

carry 8-bi t posit ive result

The carry bit remains a logic 0.


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Example

3. If we add 1110 1110 and 1111 0000, weget

1110 1110

+ 1111 0000We get 1 1101 1110

carry 8-bi t negative resu lt

This sets the carry bit and thenegative bit to log ic 1.


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Accumulator

Accumulator receives data from internaldata bus.

The accumulator also sends its contents toother devices using the internal data bus.

Is the microprocessors major workingregister.

Is always a major part of themicroprocessors programming model.

Hold data for manipulation.

Most arithmetic and logic operations ondata use both the ALU and the accumulator.


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Examples

Consider how the microprocessor adds two words, A and wordB.

- First, word A is placed in the accumulator.

- The addition is then executed by adding word B (the contents of a

memory location) to word A (in the accumulator).

- The resulting sum (C) is placed in the accumulator, replacing word

A.- The result of an ALU operation is usually placed in theaccumulator.

- The accumulators original contents are lost because they are

overwritten.

Data transfer.

(Between an I/O port and a memory location, or between onememory location and another).

- First, the data is moved from its source to the accumulator.

- Then the data is moved from the accumulator to its destination.


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Example

1) Data is found in the accumulator and in register D, neitherof which is connected to any other device at this time. Notethat the instruction register contains the instruction ADD.


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Continue2) The accumulators data is placed on the microprocessors internal data

bus.

- One of the ALUs temporary data registers is connected to the bus.- This temporary register is loaded with a copy of the data in the

accumulator.

- Only the accumulator and the temporary register use the internal databus at this time.


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Continue

3) Register Ds data is placed on the microprocessors internal data bus.

- The ALUs other temporary data register is connected to the bus.

- This temporary register is loaded with a copy of the data in register D.

- Only register D and the temporary register use the internal data bus atthis time.


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Continue

4) The ALU is directed to add the data at its input ports.

- Its output port is connected to the accumulator.

- The result of the addition is placed in the accumulator.

- Note: This addition sets the status registers negative, carry,

overflow, and intermediate carry bits

1101 1110

+ 1101 1010

1 1011 1000

carry negative


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Continue

Status Register Word

Status Register

Accumulator Register

0 1 1 1 0 1 1 1


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Continue

5) The accumulators input port and output port are both turned off.

- The sum resulting from the addition is in the accumulator, and

the status register shows the new results.

- The bus temporary registers and the instruction register are

available for another operation.

- Remember that the data bus moves data words, not bits.


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Basic Instruction Cycle

Execute

Instruction

Start

FetchInstruction

End

Fetch Cycle

Execute Cycle

PC = 0000H

PC = PC + n


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intriduction ii

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