Microprocessor archetecture

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MICROPROCESSORS

Ms. Ruchi Srivastava

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UNIT I


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Introduction to Microprocessor

• A microprocessor is a multipurpose, programmable, clock – driven, register based electronic device.

• It consists of four basic parts:• Processor• Memory• Input• Output


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Basic Block Diagram

Micro Processor

Memory

Input

Output


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Micro Processor

CPU


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CPU

Arithmetic/ Logic Unit

(ALU)

Control Unit


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Microprocessor Bus

• Address Bus• Data Bus• Control Bus


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Computer/Microprocessor Languages

• Machine Language

• Assembly Language

• High Level Languages


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Microprocessor 8085

An 8 – bit processorHaving

A 16 – bit Address Bus


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Microprocessor Architecture and its Operations

ARCHITECTURE OPERATIONS

• ALU• Register Array• Control Unit• System Bus

• Opcode Fetch• Memory Read• Memory Write• Input Read• Output Read


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Register ArrayAccumulator Flag Register

B C

D E

H L

Stack Pointer (SP)

Program Counter (PC)


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8085 PinoutX1 1 40 VCC X2 2 39 HOLD

RESET OUT 3 38 HLDA SOD 4 37 CLK (OUT) SID 5 36

TRAP 6 35 READY RST 7.5 7 34 IO/ RST 6.5 8 33 S1 RST 5.5 9 32

INTR 10 31 11 30 ALE

AD0 12 29 S0 AD1 13 28 A15 AD2 14 27 A14 AD3 15 26 A13 AD4 16 25 A12 AD5 17 24 A11 AD6 18 23 A10 AD7 19 22 A9 VSS 20 21 A8


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Pin Description• Intel 8085 is a 40 – pin IC.• The various signals on these pins can be

classified into six groups:o Address Buso Data Buso Control and Status signalso Externally Initiated signalso Serial I/O ports o Power Supply and Frequency signals


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Power Supply and Frequency Signals

Pin No. 40 – VCC

Pin No. 20 – VSS

Pin No. 01 – X1

Pin No. 02 – X2

Pin No. 37 – CLK (OUT)


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Power Supply and Frequency Signals

• VCC & VSS are the power supply pins.

• X1 and X2 are the crystal clocks. Each having a frequency of 6 MHz. The frequency is internally divided by two. So the system works at a frequency of 3 MHZ.

• CLK (OUT) is Clock Out. It is used to give system clock to other devices.


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Address & Data BusPin No. (12 – 19) – AD0 – AD7

Pin No. (21 – 28) – A8 – A15

AD0 – AD7 – Multiplexed Address/Data Bus Pin no. 12 – 19 are the multiplexed pins. They serve the purpose of address bus as well as data bus. As address bus, they serve as, lower order address bus.

A8 – A15 – Address Bus Pin no. 21 – 28, serve as, higher order address bus.


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Control and Status signals

Pin No. 29 & 33 – S0 & S1

Pin No. 30 – ALEPin No. 31 - Pin No. 30 -

Pin No. 30 – IO/

WRRDM


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Control and Status signalsS0 & S1 – are the status signals.

to identify various microprocessor operations.

ALE – Address Latch Enable It is a control signal. It is used to demultiplex the address/data bus.

It is a control signal to initiate the write operation. WR


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Control and Status signals

- It is a control signal to initiate the operation.

IO/ - It is a control signal to activate memory/IO buffer.

RD

M


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Externally Initiated Signals

Pin No. 3 – RESET OUT Pin No. 6 - TRAP

Pin No. 7 – RST 7.5Pin No. 8 – RST 6.5Pin No. 9 – RST 5.5Pin No. 10 - INTR

Pin No. 11 - Pin No. 35 - READY

Pin No. 36 - Pin No. 38 - HLDAPin No. 39 - HOLD

INTA

RESETIN


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TRAP, RST 7.5, RST 6.5, RST5.5 & INTR Are five interrupts on 8085 chip, with TRAP having highest priority, and INTR having lowest priority Except INTR, all the other four interrupts are vectored. Only INTR is non-vectored interrupt.

- is interrupt acknowledgement. This signal is initiated by the processor, to respond to

an interrupting device.

INTA


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HOLD – This signal is used by a peripheral to request the processor to gain control over the system bus.

HLDA – This signal is initiated by the microprocessor, in response to HOLD signal.

READY – Signal on this pin is sent by a slow responding peripheral, in order to delay the microprocessor


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Externally Initiated Signals - When the signal on this pin goes low,

the processor is reset.

RESET OUT – This signal s used to reset other devices, when microprocessor is being reset.

RESETIN


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Serial I/O Ports

Pin No. 4 – SODPin No. 5 – SID

There are only two pins under this category – SID – Serial Input DataSOD – Serial Output DataThese pins are used for serial input/output data transmission.


Microprocessor archetecture

Engineering

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