Computer Architecture and Fetch-execute cycle

What is the difference between address and data bus and control bus?

In the address and data buses the lines all form part of the same information. In the control bus they are simply grouped together for convenience. Each has a different function and may be used at different times.

What is instruction register?

Instruction register is used to hold the current instruction in the processor while it is being decoded and executed. It is also known as the Current Instruction Register(CIR)

What is the job of the microprocessor?

It is the job of the microprocessor which is controlling the computer , to fetch a single program instruction from the memory, decide what to do by decoding this instruction and then carry out any action which might be needed which is the execution of the instruction

What is the memory address register (MAR)?

Memory address register holds the address of the data currently in use. It is directly connected to the address bus.

What is the memory data register(MDR)?

Memory data register holds the contents of the last data that was either read or written to the memory. It is directly connected to the data bus. it is also known as memory buffer register(MBR)

What is the architecture of a computer

A von Neumann Architecture

What is the system bus?

The system bus is a cable which carries data communication between the major components of the computer including the microprocessor.

What are the four functional components of a computer?

1) Input/output 2) Memory 3) Control Unit 4) Arithmetic logic unit

Types of registers

1) Accumulator 2) Flags register (Status register) 3) Instruction Register 4) Program Counter 5) Memory Address Register (MAR) 6) Memory Buffer Register (MBR)

What are the three type of groups of wiring (bus)?

1) Data bus 2) Address bus 3) Control bus

What will a von Neumann computer do?

1) Fetch and execute a series of instructions in a program one after the other 2) Store all instructions and data currently in use in computer's memory (stored program concept) 3) Single Processor architecture

What is the steps for the fetch and execute cycle?

1) Load the address that is in the program counter (PC) into the memory address register (MAR) 2) Increment the PC by 1 3) Load the instruction that is in the memory address given by the MAR into the memory data register (MDR) 4) Load the instruction that is now in the MDR into the current instruction register (CIR) 5) Decode the instruction that is in the CIR 6) If the instruction is a jump instruction then 1)Load the address part of the instruction into the PC 2) Reset by going to step 1 7) Else 1) Execute the instruction 2) Reset the cycle by going back to the beginning of fetch decode execute cycle END IF

What are the main purpose of the control lines?

1) Read to initiate a memory read operation 2) Write to initiate a memory write operation 3) Reset clears all internal registers and starts executing instructions from a pre-defines address

Reading content from RAM

1) Set MAR to the address where to read 2) Control unit issues read signal to RAM 3) Content of memory location is transferred to MDR

What is the accumulator?

Accumulator is used for arithmetic and logic operations. It is used to hold the result of operations performed by the ALU. It is the place where the answers from many operations are stored temporarily before being put out to the computer's memory

What is a register?

A register is a memory location within the CPU itself designed to be quickly accessed for purposes of fast data retrieval.

What is flags register?

Flags register is used to record the effect of the lest ALU operation. It is also known as the status register.

What is the program counter?

Program counter (PC) holds the address of the next instruction to be fetched. It is also known as Sequence Control Register(SCR)

What is the type of memory used in Von Neumann model?

Random Access Memory (RAM)

What is ALU?

The Arithmetic Logic Unit is used to perform arithmetic and logical calculations and acts as a gateway between the processor and the rest of the system.

What is Input/Output?

The Input/Output components of a computer are hardware devices that are responsible for getting data from the computer to the user or from the user to the computer.

What is the address bus?

The address bus is a simplex bus carrying addresses where data or instructions may be found or should be stored form the processor to the memory.

what is the control bus?

The control bus carries synchronization signals to enable the various devices to co-operate in carrying out a task. There will be control signals that command the memory to read or write and numerous other signals to ensure that the system operates successfully.

What is Control Unit?

The control unit forms part of the CPU. The control unit monitors the sequencing and timing of all operations. It contains a clock that oscillates at a regular frequency when electrical power is applied. The clock emits an electronic signal for each oscillations. Each separate operation is synchronized to the clock signal

What is the data bus?

The data bus is a half duplex bus carrying data and instructions form the memory to the CPU and data form the CPU to the memory.

What is the purpose of the main memory?

The main memory is used by the computer for storing a program and its data while the program is running.

Writing to RAM

When the CPU writes to RAM , it needs to know where to write which is the address where to put the data into RAM and what to write which is data to put into RAM. This address and data are normally obtained by decoding the instruction in CIR.