Architecture SP

8/4/2019 Architecture SP

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Microprocessors

Swapnil PujariE&TC Dept., A.G.P.I.T, Solapur


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Microprocessors

What is a microprocessor?

What is a hardware?

What is a program?

What is a software?


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Microprocessor:

Microprocessor is a multipurpose, programmable,

clock-driven, register based electronic device that

reads binary instructions from a storage device

called memory, accepts binary data as input and

processes data according to those instructions, andprovides as output.

Hardware and Software:

The physical components of the system i.e.computer are called Hardware.

Group of programs is called software.


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HOW DOES THE MICROPROCESSOR

WO

RK? The Microprocessor reads

BINARY instructions from a

storage device, called

MEMORY.

It accepts binary data as input

and processes data according

to the instructions andprovides output.


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Binary Digits

The p is a device that operates in binary

digits, 0 & 1, also called as bits.

Each p recognizes & processes a group of bitscalled as word.

8-bit word is known as 8 bit p & a processor

with a 32-bit word is known as 32 bit p.


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MPU initiated operations:

MPU performs primarily 4 operations: Memory Read: Reads data (or instructions) from memory.

Memory Write: Writes data (or instructions) from memory.

I/O Read: Accepts data from input devices.

I/O Write: Sends data to output device.

To communicate with a peripheral device, MPU needs to perform

following steps:

Step 1:Identify peripheral or memory location.

Step 2:Transfer data.

Step 3: Provide timing or synchronization signals.


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Intel Microprocessors History

Intel 4004 is the first 4-bit microprocessor introduced

by Intel in 1971. After that Intel introduced its first 8-bit microprocessor8088 in 1972.

These microprocessors could not last long as general-

purpose microprocessors due to their design andperformance limitations.

In 1974, Intel introduced the first general purpose 8-bitmicroprocessor 8080 and this is the first step ofIntel

towards the development of advanced microprocessor. Later, Intel launched microprocessor 8085 with a few

more features added to its architecture, and it isconsidered to be the first functionally completemicroprocessor.


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8085 Microprocessor

The Intel 8085 is an 8 bit p introduced by Intel in1977. It was binary-compatible with the more

famous Intel 8080 but required less supporting

hardware, thus allowing simpler and less

expensive microcomputer systems to be built.

The "5" in the model number came from the fact

that the 8085 requires only a +5-volt (V) power

supply rather than the +5V, -5V and +12V suppliesthe 8080 needed.


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The salient features of8085 p

It is a 8 bit microprocessor.

It has 16 bit address bus and hence can address up

to 216 = 65536 bytes (64KB) memory locations

through A0-A15.

The first 8 lines of address bus and 8 lines of data

bus are multiplexed AD0 AD7.

Data bus is a group of8 lines D0 D7.

It supports external interrupt request.

A 16 bit program counter (PC)

A 16 bit stack pointer (SP)


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Features ctd

Six 8-bit general purpose register arranged in pairs:BC, DE, HL.

It requires a signal +5V power supply and operates at

maximum clock frequency of 3MHZ and minimum

clock frequency of500KHz.

It is enclosed with 40 pins DIP ( Dual in line

package).

It provides 5 level intrrupts.


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The 8085Bus Structure

The 8-bit 8085 MPU (Micro Processing Unit)

communicates with the other units using a 16-bit

address bus, an 8-bit data bus and a control bus.


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Address Bus

Consists of 16 address lines: A0 A15

Operates in unidirectional mode:The address bits are

always sent from the MPU to peripheral devices, not

reverse.

16 address lines are capable of addressing a total of 216 =65,536 (64k) memory locations.

Address locations: 0000 (hex) FFFF (hex)


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Data Bus

Consists of8 data lines: D0 D7 Operates in bidirectional mode:The data bits are

sent from the MPU to peripheral devices, as well as

from the peripheral devices to the MPU. Data range: 00 (hex) FF (hex)

ControlBus

Consists of various lines carrying the control signalssuch as read / write enable, flag bits


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8085 Functional Pin Diagram

40 pin DIP

+5V

3 - 5MHz ADD BUS

DATA BUS

CONTROL STATUS

POWER SUPPLY AND FREQ

EXTERNALLY INITIATED SIGNALS

SERIAL I/O PORTS


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8085 PIN DESCRIPTION

AD0-AD7: Multiplexed Address and data lines.

A8-A15:Tri-stated higher order address lines.

ALE: Address latch enable is an output signal.It goes

high when operation is started by processor .

S0,S1:These are the status signals used to indicate

type of operation.S0 S1 Operation

0 0 Halt

0 1 Memory or I/O

READ

1 0 Memory or I/O

WRITE

1 1 Opcode fetch


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8085 PIN DESCRIPTION..

RD: Read is active low input signal used to read data from I/O

device or memory. WR:Write is an active low output signal used write data on

memory or an I/O device.

READY(input):This signal is used to check the status of outputdevice.If it is low, P will WAIT until it is high.

TRAP(input):It is an Edge triggered highest priority , non maskable interrupt. After TRAP, restart occurs and execution startsfrom address 0024H.

RST5.5,6.5,7.5(inputs):These are maskable interrupts and have

low priority than TRAP. INTR(input) & INTA(out):INTR is a interrupt request signal after

which P generates INTA or interrupt acknowledge signal.

IO/M:This is output pin or signal used to indicate whether 8085is working in I/O mode(IO/M=1) or Memory mode(IO/M=0 ).


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HOLD(input)&HLDA(output):HOLD is an input signal.

When P receives HOLD signal it completes currentmachine cycle and stops executing next instruction. Inresponse to HOLD, P generates HLDA that is HOLDAcknowledge signal.

RESET IN:This is input signal. When RESETIN is low p

restarts and starts executing from location 0000H. RESETOUT:This is an active high signal output signal to

indicate that p is reset. This signal is used as system resetto reset other devices connected in system.

SID: Serial input data is input pin used to accept serial 1 bitdata under software control. It is associated with RIMinstruction.

SOD:This is a active high serial output port pin, used totransfer serial 1 bit data under software control. It is

associated with SIM instruction.


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X1X2 :These are clock input signals and are connected

to crystal, LC,or RC circuit. The frequency is divide by

two and used as operating frequency. So if 6 MHz is

connected to X1X2, the operating frequency becomes

3 MHz

CLOCK OUT:This is an output signal, used as a system

clock. The internal operating frequency is available on

CLOCK OUT pin.

VCC & VSS:Power supply VCC=+ -5Volt& VSS=-GND

reference.


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Timing diagram:MVI A,32H Instruction2000H 3EH ;MVI A, 32H

2001H 32H

00H; low-

order Add3E; opcode

T1 T2 T3 T4 T1 T2 T3

20H; high-order

address

01H; low-

order Add32H; Data

Unspecified 20H; High-order address

Status IO/M=0,S1=1,S0=1; opcode fetch Status IO/M=0,S1=1,S0=0; data read

RD

ALE

AD7-AD0

A15-A8

M1 (Opcode-fetch) M2 (Memory

Read)


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8085 Microprocessor Architecture


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8085 Architecture is divided in different groups:

Arithmetic & Logical group

Register group

Interrupt control group Serial I/O control group

Instruction register, decoder, timing & control group.


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Arithmetic and Logical group

Accumulator:

It is 8 bit general purpose register.

It is connected to ALU.

So most of the operations are done in Acc.

Temporary register:

It is not available for user

All the arithmetic and logical operations are done in thetemporary register but user cant access it.

Flag:

It is a group of5 flip flops used to know status of variousoperations done.

The Flag Register along with Accumulator is called PSW

or Program Status Word.


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Arithmetic and Logical group..

F

lag Register is given by:

S:Sign flag is set when result of an operation is negative.

Z:Zero flag is set when result of an operation is 0.

AC: Auxiliary carry flag is set when there is a carry out of lower nibble orlower four bits of the operation.

P:Parity flag is set when result contains even number of 1s.

Rest are dont care flip flops.

CY: Carry flag is set when there is carry generated by an operation.

SS ZZ XX ACAC XX PP XX CYCY


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Register Group

Temporary registers (W,Z):These are not available for user.

These are loaded only when there is an operation being

performed.

General purpose:There are six general purpose registers in8085 namely B,C,D,E,H,L.These are used for various data

manipulations.

Special purpose :There are two special purpose registers in

8085:

1. SP :Stack Pointer.

2. PC:Program Counter.


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Register Group..

Stack Pointer:

This is a 16 bit register used to define the stack starting address. Itis a reserved portion of memory where register pair informationcan be stored or taken back under software control. It is used tokeep track of data stored on stack.

Program Counter:

It is 16 bit register used to point the location from which the nextinstruction is to be fetched.

When a single byte instruction is executed PC is automaticallyincremented by 1.

Upon reset PC contents are set to 0000H and next instruction isfetched onwards.

Increment/Decrement Latch:

It is a 16 bit register used in coordination with PC & SP, toincrement or decrement the contents of PC/SP registers.


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INTERRUPT CONTROL

It accepts different interrupts like TRAP INT5.5,6.5,7.5and INTR. When a valid interrupt request is present it informs control logic to

take action in response to each signal.

SERIAL IO CONTROL GROUP

The data transferred on D0-D7 lines is parallel data, but under

certain condition it is advantageous to use serial data transfer.

8085 accepts or transfers the serial 1 bit data by using SID and

SOD signals and it can be performed by using SIM & RIM

instructions.


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INSTRUCTION REGISTER,DECODER & CONTROL

Instruction register: When an instruction is fetched , it

is loaded in instruction register. These contents are then

provided to decoder for decoding. This register takes

the opcode value only. Its a non programmable register.

Instruction decoder:It decodes the instruction from

instruction register and then gives decoded information

to control block.

Timing and control:This is the control section ofp. Itaccepts clock input .


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Demultiplexing of Address & Data Bus

A15-A8

LatchAD7-AD0

D7

- D0

A7- A08085

ALE


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