File Name: central processing unit in computer organization and architecture .zip
In computer engineering , computer architecture is a set of rules and methods that describe the functionality, organization, and implementation of computer systems. Some definitions of architecture define it as describing the capabilities and programming model of a computer but not a particular implementation. The first documented computer architecture was in the correspondence between Charles Babbage and Ada Lovelace , describing the analytical engine.
The term 'computer architecture' is sometimes referred only to Instruction set design Circuit design Hardware design Pipelining.
Home About My account Contact Us. Stack Organization Introduction 3. So you're shopping for a new computer in an electronics store and you're trying to make sense of the technical specifications. Sounds impressive, but what does it really mean? The CPU is often simply referred to as the processor.
The block diagram of processor unit is shown in figure below where all registers are connected through common buses. The registers communicate each other not only for direct data transfer but also while performing various micro-operations.
Here two sets of multiplexers select register which perform input data for ALU. A decoder selects destination register by enabling its load input. The function select in ALU determines the particular operation that to be performed. Compiled By: Er. Hari Aryal [haryal4 gmail. It consists of a program counter, instruction register, timing and control logic.
The control logic may be either hardwired or micro-programmed. If it is a hardwired, register decodes and a set of gates are connected to provide the logic that determines the action required to execute various instructions.
A micro-programmed control unit uses a control memory to store micro instructions and a sequence to determine the order by which the instructions are read from control memory. The control unit decides what the instructions mean and directs the necessary data to be moved from memory to ALU. Control unit must communicate with both ALU and main memory and coordinates all activities of processor unit, peripheral devices and storage devices.
Control unit must have inputs that allow determining the state of system and outputs that allow controlling the behavior of system. This clock pulse is also called as processor cycle time or clock cycle time. All these control signals are applied directly as binary inputs to individual logic gate. Fig: Control Unit 2. They serve two functions: 1. User-Visible Registers - enable the machine- or assembly-language programmer to minimize main-memory references by optimizing use of registers 2.
Push, pop, and other stack instructions need not contain an explicit stack operand. Figure indicates in general in general term how ALU is interconnected with rest of the processor. Data are presented to ALU in register and the result of operation is stored in register. These registers are temporarily storage location within the processor that are connected by signal path to the ALU.
The ALU may also set flags as the result of an operation. The flags values are also stored in registers within the processor. The design of ALU has three stages. Design the arithmetic section The basic component of arithmetic circuit is a parallel adder which is constructed with a number of full adder circuits connected in cascade. By controlling the data inputs to the parallel adder, it is possible to obtain different types of arithmetic operations. Below figure shows the arithmetic circuit and its functional table.
Below figure shows a circuit that generates four basic logic micro-operations. It consists of four gates and a multiplexer. Each of four logic operations is generated through a gate that performs the required logic. The two selection input S1 and S0 choose one of the data inputs of the multiplexer and directs its value to the output. Functional table lists the logic operations. Combine these 2 sections to form the ALU Below figure shows a combined circuit of ALU where n data input from A are combined with n data input from B to generate the result of an operation at the G output line.
ALU has a number of selection lines used to determine the operation to be performed. The selection lines are decoded with the ALU so that selection lines can specify distinct operations. The mode select S2 differentiate between arithmetic and logical operations. The two functions select S1 and S0 specify the particular arithmetic and logic operations to be performed. With three selection lines, it is possible to specify arithmetic operation with S2 at 0 and logical operation with S2 at 1.
These ordered steps are the instructions. Computer instructions are stored in central memory locations and are executed sequentially one at a time. The control reads an instruction from a specific address in memory and executes it.
It then continues by reading the next instruction in sequence and executes it until the completion of the program. A computer usually has a variety of Instruction Code Formats. It is the function of the control unit within the CPU to interpret each instruction code and provide the necessary control functions needed to process the instruction. An n bit instruction that k bits in the address field and m bits in the operation code field come addressed 2k location directly and specify 2m different operation.
The bits that define the mode field of an instruction code specify a variety of alternatives for choosing the operands from the given address. Operation specified by an instruction is executed on some data stored in the processor register or in the memory location.
Operands residing in memory are specified by their memory address. Operands residing in processor register are specified with a register address. The instruction format in this type of computer uses one address field.
General register organization:- The instruction format in this type of computer needs three register address fields.
This operation has the effect of popping the 2 top numbers from the stack, operating the numbers and pushing the sum into the stack. For example: ADD Computers may have instructions of several different lengths containing varying number of addresses. Following are the types of instructions. Three address Instruction With this type of instruction, each instruction specifies two operand location and a result location. A temporary location T is used to store some intermediate result so as not to alter any of the operand location.
The three address instruction format requires a very complex design to hold the three address references. Two address instruction Two-address instructions are the most common in commercial computers. Here again each address field can specify either a processor register, or a memory word. One address must do double duty as both operand and result. The two address instruction format reduces the space requirement.
To avoid altering the value of an operand, a MOV instruction is used to move one of the values to a result or temporary location T, before performing the operation. One address Instruction It was generally used in earlier machine with the implied address been a CPU register known as accumulator.
The accumulator contains one of the operand and is used to store the result. One-address instruction uses an implied accumulator Ac register for all data manipulation.
All operations are done between the AC register and a memory operand. The symbol M[A] denotes the operand at memory address symbolized by A. In fact, all register reference instructions that use an accumulator are implied-mode instructions.
Instruction Opcode Advantage: no memory reference. In other words, an immediate-mode instruction has an operand field rather than an address field. The operand field contains the actual operand to be used in conjunction with the operation specified in the instruction.
When the address field specifies a processor register, the instruction is said to be in register-mode. Advantage: no memory reference. The address field of the instruction uses fewer bits to select a register than would have been required to specify a memory address directly. In some computers it is automatically accessed.
The operand resides in memory and its address is given directly by the address field of the instruction. Disadvantage: Complexity Compiled By: Er. The stack pointer is maintained in register. These instructions perform arithmetic, logic and shift operations. Arithmetic Instructions Compiled By: Er. These instructions specify conditions for altering the content of the program counter.
The change in value of program counter as a result of execution of program control instruction causes a break in sequence of instruction execution. Some typical program control instructions are: Compiled By: Er. The last instruction of every subroutine, commonly called return from subroutine; transfer the return address from the temporary location into the program counter.
This results in a transfer of program control to the instruction where address was originally stored in the temporary location. Other are , , 80x86 etc. It is classified as a reduced instruction set computer RISC.
Load A Store C 0-address instructions e. PC is incremented by length of instruction just completed. After an instruction is fetched from memory, the PC is automatically incremented to hold the address of, or point to, the next instruction to be executed. Instruction Register IR holds the most recently read instruction from memory while it is being decoded by the Instruction Interpreter. Buffer is referring to temporarily holding data.
In this chapter: Chap. 8. ○ Describe the organization and architecture of the CPU with an emphasis on the user's view of the computer. ○ User who programs.
In computer engineering , computer architecture is a set of rules and methods that describe the functionality, organization, and implementation of computer systems. Some definitions of architecture define it as describing the capabilities and programming model of a computer but not a particular implementation. The first documented computer architecture was in the correspondence between Charles Babbage and Ada Lovelace , describing the analytical engine. When building the computer Z1 in , Konrad Zuse described in two patent applications for his future projects that machine instructions could be stored in the same storage used for data, i.
It is a multipurpose, programmable, clockdriven, register based electronic device - that accepts binary data as input, processes it according to instructions stored in its memory, and provides results as output. A CPU.
Its purpose is to interpret instruction cycles received from memory and perform arithmetic, logic and control operations with data stored in internal register, memory words and I/O interface units. A CPU is usually divided into two parts namely processor unit (Register Unit and Arithmetic Logic Unit) and control unit.