06-11-2012, 11:21 AM
Introduction to 8085 Microprocessor
[attachment=38261]
Digital Computer
A digital computer is a programmable machine specially designed for making computation
Its main components are
CPU (Central Processing Unit)
Memory
Input device
Output device
CPU
The major sections of a CPU
Arithmetic and Logic Unit (ALU)
Accumulator
General and Special purpose registers
Timing and Control Unit
CPU
The function of an ALU is to perform arithmetic operations such as addition and subtraction; and logical operations such as AND, OR and EXCLUSIVE-OR
Timing and control unit controls the entire operations of a computer
The accumulator is a register, which contains one of the operands and stores results of most arithmetic and logical operations
General purpose registers are used for temporary storage of data and intermediate results while computer is making execution of a program
Special purpose registers are used by the microprocessor itself
Memory & I/O
The memory is a storage device. It stores program, data, results etc
The computer receives data and instructions through input devices
The computer sends results to output devices
Microprocessor
With the advent of LSI and VLSI technology it became possible to build the entire CPU on a single chip IC
A CPU built into a single LSI/VLSI chip is called a microprocessor
A digital computer using microprocessor as its CPU is called a microcomputer
The term micro initiates its physical size; not it’s computing power
Today the computing power of a powerful microprocessor approaches that a CPU on earlier large computer
The main sections of a microprocessor are: ALU, timing and control unit, accumulator, general purpose and special purpose registers
8085 Microprocessor
Intel 8085 is an 8-bit, N-channel Metal Oxide semiconductor (NMOS) microprocessor
It is a 40 pin IC package fabricated on a single Large Scale Integration (LSI) chip
The Intel 8085 uses a single +5V DC supply for its operation
Its clock speed is about 3MHz
The clock cycle is of 320 ns
The time for the clock cycle of the Intel 8085 is 200 ns
It has 80 basic instructions and 246 opcodes
General Registers
The 8085 has six general-purpose registers to store 8-bit data; these are identified as B, C, D, E, H, and L
They can be combined as register pairs - BC, DE, and HL - to perform some 16-bit operations
The programmer can use these registers to store or copy data into the registers by using data copy instructions
The HL register pair is also used to address memory locations
In other words, HL register pair plays the role of memory address register
Accumulator & Pointers
The accumulator is an 8-bit register that is a part of arithmetic/logic unit (ALU)
Program Counter - Deals with sequencing the execution of instructions. Acts as a memory pointer
Stack Pointer – Points to a memory location in R/W memory, called the stack
Instruction Register/Decoder
The instruction register and the decoder are considered as a part of the ALU
The instruction register is a temporary storage for the current instruction of a program
The decoder decodes the instruction and establishes the sequence of events to follow
Flags
The ALU includes five flip-flops, which are set or reset after an operation according to data conditions of the result in the accumulator and other registers
They are called Zero (Z), Carry (CY), Sign (S), Parity (P), and Auxiliary Carry (AC) flags
Conversion and Execution
Convert the mnemonics into Hex code; we need to look up the code in 8085 instruction set.
Store the program in Read/Write memory of a single-board microcomputer. This may require the knowledge about memory addresses and the output port addresses.
Finally execute the program.
[attachment=38261]
Digital Computer
A digital computer is a programmable machine specially designed for making computation
Its main components are
CPU (Central Processing Unit)
Memory
Input device
Output device
CPU
The major sections of a CPU
Arithmetic and Logic Unit (ALU)
Accumulator
General and Special purpose registers
Timing and Control Unit
CPU
The function of an ALU is to perform arithmetic operations such as addition and subtraction; and logical operations such as AND, OR and EXCLUSIVE-OR
Timing and control unit controls the entire operations of a computer
The accumulator is a register, which contains one of the operands and stores results of most arithmetic and logical operations
General purpose registers are used for temporary storage of data and intermediate results while computer is making execution of a program
Special purpose registers are used by the microprocessor itself
Memory & I/O
The memory is a storage device. It stores program, data, results etc
The computer receives data and instructions through input devices
The computer sends results to output devices
Microprocessor
With the advent of LSI and VLSI technology it became possible to build the entire CPU on a single chip IC
A CPU built into a single LSI/VLSI chip is called a microprocessor
A digital computer using microprocessor as its CPU is called a microcomputer
The term micro initiates its physical size; not it’s computing power
Today the computing power of a powerful microprocessor approaches that a CPU on earlier large computer
The main sections of a microprocessor are: ALU, timing and control unit, accumulator, general purpose and special purpose registers
8085 Microprocessor
Intel 8085 is an 8-bit, N-channel Metal Oxide semiconductor (NMOS) microprocessor
It is a 40 pin IC package fabricated on a single Large Scale Integration (LSI) chip
The Intel 8085 uses a single +5V DC supply for its operation
Its clock speed is about 3MHz
The clock cycle is of 320 ns
The time for the clock cycle of the Intel 8085 is 200 ns
It has 80 basic instructions and 246 opcodes
General Registers
The 8085 has six general-purpose registers to store 8-bit data; these are identified as B, C, D, E, H, and L
They can be combined as register pairs - BC, DE, and HL - to perform some 16-bit operations
The programmer can use these registers to store or copy data into the registers by using data copy instructions
The HL register pair is also used to address memory locations
In other words, HL register pair plays the role of memory address register
Accumulator & Pointers
The accumulator is an 8-bit register that is a part of arithmetic/logic unit (ALU)
Program Counter - Deals with sequencing the execution of instructions. Acts as a memory pointer
Stack Pointer – Points to a memory location in R/W memory, called the stack
Instruction Register/Decoder
The instruction register and the decoder are considered as a part of the ALU
The instruction register is a temporary storage for the current instruction of a program
The decoder decodes the instruction and establishes the sequence of events to follow
Flags
The ALU includes five flip-flops, which are set or reset after an operation according to data conditions of the result in the accumulator and other registers
They are called Zero (Z), Carry (CY), Sign (S), Parity (P), and Auxiliary Carry (AC) flags
Conversion and Execution
Convert the mnemonics into Hex code; we need to look up the code in 8085 instruction set.
Store the program in Read/Write memory of a single-board microcomputer. This may require the knowledge about memory addresses and the output port addresses.
Finally execute the program.