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Instruction cycle with indirect?
In an instruction cycle with indirect addressing, the CPU fetches the instruction, decodes it to determine the memory address of the operand stored in a register, fetches the operand from the memory location pointed to by the register, and executes the instruction using the operand. Finally, the CPU stores the result back in memory if needed. This extra step of fetching the operand based on the indirect memory address adds complexity to the instruction cycle.
How do the contents of the MAR and MDR registers changes during the fetch decode execute cycle?
During the fetch-decode-execute cycle, the Memory Address Register (MAR) holds the address of the memory location from which data is to be fetched or to which data is to be written. In the fetch phase, the MAR is loaded with the address of the next instruction to be executed. The Memory Data Register (MDR) then temporarily holds the data fetched from memory or the data to be written to memory. As the cycle progresses, the contents of the MAR and MDR are updated based on the memory operations required for executing the instruction.
How does the CPU keep track of which instruction to execute next?
The instruction register holds a pointer to the current instruction (in working memory) while the next instruction register points to the next instruction (the first instruction immediately after the current instruction's operands). If the current instruction is a jump instruction, it can change the next instruction register, allowing the program to branch to a new instruction once the jump instruction is processed. The next instruction pointer is automatically moved into the current instruction register once the current instruction has been processed. The entire process of executing an instruction is known as the fetch-decode-execute cycle.
How does fetch decode cycle work?
The program counter in the processor holds the address of the next instruction needed from main memory. The program counter copies its contents into the memory address register. The memory address register then sends the address along the address bus to main memory and the contents of the memory location specified by the address are sent along the data bus to the memory buffer register. The contents of the memory buffer register are then copied to the current instruction register where they are decoded and executed.
What is the definition of fetch cycle?
Fetch cycle is defined as a part of instruction cycle in which data is fetched from the memory pointed by Holds the address of a memory block to be read from or written to) and stores the data in MDR( a two-way register that holds data fetched from memory (and ready for the CPU to process) or data waiting to be stored in memory) for further processing. Instruction cycle= Fetch cycle+ Execute cycle
How does fetch decode execute cycle work?
The program counter in the processor holds the address of the next instruction needed from main memory. The program counter copies its contents into the memory address register. The memory address register then sends the address along the address bus to main memory and the contents of the memory location specified by the address are sent along the data bus to the memory buffer register. The contents of the memory buffer register are then copied to the current instruction register where they are decoded and executed.
What is the function of instruction register?
The Instruction Register (IR) stores the instruction currently being executed. In simple processors each instruction to be executed is loaded into the instruction register which holds it while it is decoded, prepared and ultimately executed.
Why register to register instruction is faster?
Register to register addressing mode is faster because you don't have to do an extra memory access cycle or more.Register to register addressing mode is faster because:Registers are part of and are directly accessibility by the CPU assembly.They electronics that make up a register use more expensive but faster circuitry.Since it does not require memory access, the steps and time involved in memory address decoding and memory access are skipped.
What is a fetch as a cycles in a CPU?
The first part of the instruction execution cycle is the fetch cycle. Tnstruction cycle Each computer's CPU can have different cycles based on different instruction sets, but will be similar to the following cycle: 1. Fetch the instruction The next instruction is fetched from the memory address that is currently stored in the Program Counter (PC), and stored in the Instruction register (IR). At the end of the fetch operation, the PC points to the next instruction that will be read at the next cycle. 2. Decode the instruction The decoder interprets the instruction. During this cycle the instruction inside the IR (instruction register) gets decoded. 3.In case of a memory instruction (direct or indirect) the execution phase will be in the next clock pulse. If the instruction has an indirect address, the effective address is read from main memory, and any required data is fetched from main memory to be processed and then placed into data registers(Clock Pulse: T3). If the instruction is direct, nothing is done at this clock pulse. If this is an I/O instruction or a Register instruction, the operation is performed (executed) at clock Pulse. 4. Execute the instruction The Control Unit of CPU passes the decoded information as a sequence of control signals to the relevant function units of the CPU to perform the actions required by the instruction such as reading values from registers, passing them to the ALU to perform mathematical or logic functions on them, and writing the result back to a register. If the ALU is involved, it sends a condition signal back to the CU.
What is a data instruction register?
A Data Instruction Register (DIR) is a component within a computer's CPU that temporarily holds instructions fetched from memory before they are executed. It helps in decoding and executing the instruction by providing the necessary data to the control unit. The DIR plays a crucial role in the instruction cycle, ensuring that the CPU processes commands efficiently. By holding the instruction, it allows for a streamlined flow of data between memory and processing units.
How would you describe the fetch execute cycle?
Fetch Execute Cycle A more complete form of the Instruction Fetch Execute Cycle can be broken down into the following steps: 1. Fetch Cycle 2. Decode Cycle 3. Execute Cycle 4. Interrupt Cycle 1. Fetch Cycle The fetch cycle begins with retrieving the address stored in the Program Counter (PC). The address stored in the PC is some valid address in the memory holding the instruction to be executed. (In case this address does not exist we would end up causing an interrupt or exception).The Central Processing Unit completes this step by fetching the instruction stored at this address from the memory and transferring this instruction to a special register - Instruction Register (IR) to hold the instruction to be executed. The program counter is incremented to point to the next address from which the new instruction is to be fetched. 2. Decode Cycle The decode cycle is used for interpreting the instruction that was fetched in the Fetch Cycle. The operands are retrieved from the addresses if the need be. 3. Execute Cycle This cycle as the name suggests, simply executes the instruction that was fetched and decoded
What is CIR register?
The CIR (Current Instruction Register) is a crucial component of a computer's CPU that holds the instruction currently being executed. When an instruction is fetched from memory, it is placed in the CIR before being decoded and executed by the control unit. This allows the CPU to keep track of the instruction flow and manage execution efficiently. By storing the instruction temporarily, the CIR plays a key role in the instruction cycle of the CPU.
