ROHINI COLLEGE OF ENGINEERING & TECHNOLOGY
1.2 ARCHITECTURE OF INTEL 8085 MICROPROCESSOR
Features of 8085
• Intel 8085 is an 8-bit, NMOS microprocessor.
• It is a 40 pin I.C. package fabricated on a single LSI chip.
• The Intel 8085 uses a single +5Vd.c. supply for its operation
• Its clock speed is about 3 MHz The clock cycle is of 320 ns.
• It has 80 basic instructions and 256 opcodes.
Figure 1.2.1 shows the functional block diagram of Intel 8085. It consists of three main
sections:
[1] Arithmetic and Logic Unit (ALU)
[2] Timing & Control Unit [3] Set of registers.
Figure 1.2.1 Architecture 8085 processor
[Source: “Microprocessor Architecture Programming and Application” by R.S. Gaonkar, page-72]
1. ALU (Arithmetic & Logic Unit):
EE8551 MICROPROCESSOR AND MICROCONTROLLER
, ROHINI COLLEGE OF ENGINEERING & TECHNOLOGY
As the name suggest, ALU i.e arithmetic & logic unit performs the following
arithmetic & logical opeartions:
i. Addition ii.
Subtraction iii. Logical
AND iv. Logical OR
v. Logical EXCLUSIVE OR vi.
Complement (logical NOT) vii.
Increment (add 1) viii. Decrement (Subtract
1) ix. Left shift, Rotate left, Rorate
Right x. Cler, etc.
2. Timing & Control Unit:
• It generates timing & control signals which are necessary for the execution of
instructions.
• It controls data flow between CPU and peripherals including memory.
• It provides status, control and timing signals which are required for the operation
of memory and I/O devices.
• It controls entire operations of the microprocessor and peripherals connected to it.
• Thus it is seen that the control unit of the CPU acts as the brain of the computer
system.
3. Set of Registers:
• Fig 1.2.1 shows the various registers of Intel 8085 which are used by the
microprocessor for temporary storage and manipulation of data and intsructions.
• Intel 8085 microprocessor has the following registers:
i. One 8-bit Accumulator (ACC) i.e register A ii. Six 8-
bit general purpose registers. These are B, C, D, E, H & L
iii. One 16-bit stack pointer, SP iv. One 16-bit
program Counter, PC
v. Intruction register vi.
Temporary register
EE8551 MICROPROCESSOR AND MICROCONTROLLER
1.2 ARCHITECTURE OF INTEL 8085 MICROPROCESSOR
Features of 8085
• Intel 8085 is an 8-bit, NMOS microprocessor.
• It is a 40 pin I.C. package fabricated on a single LSI chip.
• The Intel 8085 uses a single +5Vd.c. supply for its operation
• Its clock speed is about 3 MHz The clock cycle is of 320 ns.
• It has 80 basic instructions and 256 opcodes.
Figure 1.2.1 shows the functional block diagram of Intel 8085. It consists of three main
sections:
[1] Arithmetic and Logic Unit (ALU)
[2] Timing & Control Unit [3] Set of registers.
Figure 1.2.1 Architecture 8085 processor
[Source: “Microprocessor Architecture Programming and Application” by R.S. Gaonkar, page-72]
1. ALU (Arithmetic & Logic Unit):
EE8551 MICROPROCESSOR AND MICROCONTROLLER
, ROHINI COLLEGE OF ENGINEERING & TECHNOLOGY
As the name suggest, ALU i.e arithmetic & logic unit performs the following
arithmetic & logical opeartions:
i. Addition ii.
Subtraction iii. Logical
AND iv. Logical OR
v. Logical EXCLUSIVE OR vi.
Complement (logical NOT) vii.
Increment (add 1) viii. Decrement (Subtract
1) ix. Left shift, Rotate left, Rorate
Right x. Cler, etc.
2. Timing & Control Unit:
• It generates timing & control signals which are necessary for the execution of
instructions.
• It controls data flow between CPU and peripherals including memory.
• It provides status, control and timing signals which are required for the operation
of memory and I/O devices.
• It controls entire operations of the microprocessor and peripherals connected to it.
• Thus it is seen that the control unit of the CPU acts as the brain of the computer
system.
3. Set of Registers:
• Fig 1.2.1 shows the various registers of Intel 8085 which are used by the
microprocessor for temporary storage and manipulation of data and intsructions.
• Intel 8085 microprocessor has the following registers:
i. One 8-bit Accumulator (ACC) i.e register A ii. Six 8-
bit general purpose registers. These are B, C, D, E, H & L
iii. One 16-bit stack pointer, SP iv. One 16-bit
program Counter, PC
v. Intruction register vi.
Temporary register
EE8551 MICROPROCESSOR AND MICROCONTROLLER
