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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