1 Microprocessor Architecture

8/9/2019 1 Microprocessor Architecture

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Microprocessor architecture


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•

• Manipulates data

and

communicate

with

•

Operates on

predesigned

set

of

instructions

• Architecture refers to the logic design of the

microprocessor


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•

perform functions

on

given

data

by

writing

– Reads one instruction at a time, matches it with

manipulation specified

– Result is stored back into memor or dis la ed on

an output device


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•

microprocessor

–

– Internal operations

–


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•

• Memory write

• I O rea get ata rom a input evice

• I/O write

(send

data

to

a output

device)

with a peripheral or memory location


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–

•

microprocessor and

peripheral

devices

consist

– Identify peripheral or memory location (using it’s

– Transfer information (data/instruction in binary

form

– Provide timing and synchronization details


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•

(communication lines)

to

perform

its

– Address bus

–

– Control bus


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• 16 bits wide A0 A1 … A15

– 8085 can

access

locations

with

numbers

from

0 to

65536, A total of 64K addresses

• Unidirectional

– Information

flows

out

of

the

microprocessor

and

into

• When 8085 wants to access a peripheral or a ‐

,

the address bus and then sends the appropriate control signals


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• , , …,

• Bi‐directional

– n ormat on ows ot ways etween t e

microprocessor and memory or I/O

• uses e a a us o rans er e nary

information (data)

• 8085 can

manipulate

8 bits

of

data

at

‐a‐time

• Width of data bus == n bit microprocessor


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•

signals –

– Timing signals

–

– I/O read/write signal


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• Micro rocessor laces the 16‐bit address of the

memory location

on

the

address

bus

• Microprocessor activates a control signal called “memory read” which enables the memory chip

• The memory

decodes

the

address

and

identifies

the right location

• The memory places the contents on the data bus

• The microprocessor

reads

the

value

of

the

data

bus after a certain amount of time


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•

• Arithmetic and

logic

operation

• Test or con itions

• Sequencing the

execution

of

program

• Storing data temporarily in stack


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•

– Used for

storing

the

result

of

any

operation

•

– Used by ALU to convey some information (zero, carry,

etc.

• B, C, D, E, H, L

–

• H, L


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•

execution

•

16 bits

wide


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•

• The memory

this

register

points

to

is

a special

•

Stack

is

used

to

hold

data

that

will

be

retr eve soon

• stack is usually accessed in a Last In First Out

(LIFO) fashion

• Used for intermediate data transfer b ALU


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2000 06 MVI B, 76’h

2001 78

2002 3E MVI A, F2’h

2004 80 ADD B

2005 76 HLT


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•

– 8085 has

a pin

called

RDY.

This

pin

is

used

by

up.

– As lon as the RDY in is low the 8085 will be in a

wait state


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•

– 8085 has

a pin

called

HOLD.

This

pin

is

used

by

.

– When the HOLD signal is activated by an external

device the 8085 sto s executin instructions and

stops using the busses.

– This allows external devices to control the

information on

the

busses,

example

DMA

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