Intel 8085 Micro Processor
- Intel 8085 is an Eight bit (8 bit) NMOS (n-type Metal Oxide Semiconductor
type) Microprocessor.
- It has 40 Pin on chip.
- This package is made on a
single LSI (Large Scale Integrated) chip.
- The Intel 8085 requires +5V Dc supply
for its operation.
- Its clock speed is about 3MHz.
- The clock cycle is of 320ns.
- This microprocessor has 80
basic instruction and 246 Op-Codes (Operation Codes).
Internal
Architecture (Figure):
Internal
Architecture (In Detail):
1.
Arithmetic
& Logic Unit (ALU)
·
ALU
handles all kind of Arithmetical and Logical Operation.
·
It
performs-
o Addition and Subtraction
o Logic-AND, Logic-OR, Logic-XOR and
Logic-NOT operation
o Increment and Decrement Operations
o Left Shift, Right Shift, Rotate
Left, Rotate Right operation
o Clear
·
ALU
receives input from Accumulator and Temperary Register, and sends output to
Internal Bus to store the value in different register location.
·
The
output helps in change of status flags and is sent to Accumulator.
2.
Timing
and Controlling Unit
·
It
is a section of CPU.
·
Data
flow between CPU and Peripheral is controlled by it.
·
The
entire operations of Microprocessor and peripheral connected to it is
controlled by Timing and Controlling Unit.
·
It
is seen that control unit of CPU acts as the brain of a computer system.
3.
Registers:
·
Registers
are used as a temporary storage system by microprocessor.
·
It
is also used for Manipulation of Data and instructions.
·
Data
saves/stores in the registers till they are sent to the memory or i/o devices
·
Intel
8085icroprocessor has 6 type of registers. They are –
o
Accumulator – 1 (8 bit)
ü It is associated with ALU.
ü It is also known as ‘A’ or ‘Acc’.
ü It is used to hold one of operand of
Arithmetic or Logical operation.
ü It serves as one input of ALU.
ü The final result of an Arithmetic or
Logical operation is stored in Accumulator.
o
Temporary
Register (8 bit)
ü It is associated with the ALU.
ü It holds data during Arithmetic or
Logical operation.
ü It is not accessible to user.
ü It is used by microprocessor and not
accessible to programmer.
o
General
Purpose Registers (8 bit)
ü 8085 microprocessor has six general
purpose registers. They are B, C, D, E, H & L.
ü To store sixteen-bit (16 bit) data,
the combination of two register is done like B-C, D-E and H-L.
ü The H-L pair is also used to act as
a memory pointer to hold a 16-bit address.
o
Program
Counter (16 bit)
ü It is used to hold the memory address
of the next instruction to be executed.
o
Stack
Pointer (16 bit)
ü It is a stacking system to store
data of Accumulator, Flags, Program Counter and General-Purpose Registers.
ü It is a sequence of memory location
being det by programmer.
ü Stack works in L-I-F-O formats. L-I-F-O
means Last IN First Out.
ü The pointer which address the stack
is known as stack pointer.
o
Instruction
Register
ü Instruction Register holds the
op-code of the instruction.
4.
Status
Flag
·
8085
Microprocessor has five status flags. These are-
o
Carry
Flag (CS) – [CP = 1 (Have Carry), CP = 0 (No Carry)]
o
Parity
Flag (P)
o
Auxiliary
Carry Flag (AC) – [AC = 1 (Have Auxiliary Carry), AC = 0 (No Auxiliary Carry)]
o
Zero
Flag (Z) – [Z = 1 (Result = 0), Z = 0 (Result is not Zero)]
o
Sign
Flag (S) – [S = 0 (+Ve), S =1 (-Ve)]
5.
Program
Status Word (PSW)
6.
Data
or Address Bus
·
8085
Microprocessor has an 8-bit data bus and 16-bit address bus.
·
Pin
A8 to A15 is used for transmitting 8 most significant
Bits (MSB) of sixteen address.
·
The
eight least significant bit (LSB) of the address are transmitted by address/data
bus (AD0 – AD7)
Intel 8085 Micro Processor
- Intel 8085 is an Eight bit (8 bit) NMOS (n-type Metal Oxide Semiconductor
type) Microprocessor.
- It has 40 Pin on chip.
- This package is made on a
single LSI (Large Scale Integrated) chip.
- The Intel 8085 requires +5V Dc supply
for its operation.
- Its clock speed is about 3MHz.
- The clock cycle is of 320ns.
- This microprocessor has 80 basic instruction and 246 Op-Codes (Operation Codes).
Internal Architecture (Figure):
Internal Architecture (In Detail):
1.
Arithmetic
& Logic Unit (ALU)
·
ALU
handles all kind of Arithmetical and Logical Operation.
·
It
performs-
o Addition and Subtraction
o Logic-AND, Logic-OR, Logic-XOR and
Logic-NOT operation
o Increment and Decrement Operations
o Left Shift, Right Shift, Rotate
Left, Rotate Right operation
o Clear
·
ALU
receives input from Accumulator and Temperary Register, and sends output to
Internal Bus to store the value in different register location.
·
The
output helps in change of status flags and is sent to Accumulator.
2.
Timing
and Controlling Unit
·
It
is a section of CPU.
·
Data
flow between CPU and Peripheral is controlled by it.
·
The
entire operations of Microprocessor and peripheral connected to it is
controlled by Timing and Controlling Unit.
·
It
is seen that control unit of CPU acts as the brain of a computer system.
3.
Registers:
·
Registers
are used as a temporary storage system by microprocessor.
·
It
is also used for Manipulation of Data and instructions.
·
Data
saves/stores in the registers till they are sent to the memory or i/o devices
·
Intel
8085icroprocessor has 6 type of registers. They are –
o
Accumulator – 1 (8 bit)
ü It is associated with ALU.
ü It is also known as ‘A’ or ‘Acc’.
ü It is used to hold one of operand of
Arithmetic or Logical operation.
ü It serves as one input of ALU.
ü The final result of an Arithmetic or
Logical operation is stored in Accumulator.
o
Temporary
Register (8 bit)
ü It is associated with the ALU.
ü It holds data during Arithmetic or
Logical operation.
ü It is not accessible to user.
ü It is used by microprocessor and not
accessible to programmer.
o
General
Purpose Registers (8 bit)
ü 8085 microprocessor has six general
purpose registers. They are B, C, D, E, H & L.
ü To store sixteen-bit (16 bit) data,
the combination of two register is done like B-C, D-E and H-L.
ü The H-L pair is also used to act as
a memory pointer to hold a 16-bit address.
o
Program
Counter (16 bit)
ü It is used to hold the memory address
of the next instruction to be executed.
o
Stack
Pointer (16 bit)
ü It is a stacking system to store
data of Accumulator, Flags, Program Counter and General-Purpose Registers.
ü It is a sequence of memory location
being det by programmer.
ü Stack works in L-I-F-O formats. L-I-F-O
means Last IN First Out.
ü The pointer which address the stack
is known as stack pointer.
o
Instruction
Register
ü Instruction Register holds the
op-code of the instruction.
4.
Status
Flag
·
8085
Microprocessor has five status flags. These are-
o
Carry
Flag (CS) – [CP = 1 (Have Carry), CP = 0 (No Carry)]
o
Parity
Flag (P)
o
Auxiliary
Carry Flag (AC) – [AC = 1 (Have Auxiliary Carry), AC = 0 (No Auxiliary Carry)]
o
Zero
Flag (Z) – [Z = 1 (Result = 0), Z = 0 (Result is not Zero)]
o
Sign
Flag (S) – [S = 0 (+Ve), S =1 (-Ve)]
5.
Program
Status Word (PSW)
6.
Data
or Address Bus
·
8085
Microprocessor has an 8-bit data bus and 16-bit address bus.
·
Pin
A8 to A15 is used for transmitting 8 most significant
Bits (MSB) of sixteen address.
·
The
eight least significant bit (LSB) of the address are transmitted by address/data
bus (AD0 – AD7)
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