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What is the consists in the Instruction register?
The Instruction Register contains the current instruction being executed. It is an internal, special register, and you can not do anything explicit with it. If you are referring to the Program Counter, that simply contains the address of the next instruction to execute. It is incremented for each opcode and operand byte fetched.
What register points to the next instruction?
actually register holds the data..there are 6 register which are temporary registers..program counter holds the address of next instruction to be fetched..instruction register holds the currently executed data...
What are the four distinct actions that a machine instruction can specify?
• The processor fetches the instruction from memory • Program counter (PC) holds address of the instruction to be fetched next • PC is incremented after each fetch • Fetched instruction loaded into instruction register
What registers is used to keep track of address of the memory location where the next instruction is located?
Instruction pointer (IP) is used to hold the offset of the next instruction to be fetched for BIU available from Code Segment whose base address is held in CS segment base register..
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
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 you calculate the physical address in 8086 microprocessor with example?
The physical address in the 8086/8088 is calculated by adding the effective address with the contents of one of the segment registers left shifted by 4 bit positions. This results in a 20 bit address bus. As an example, if the CS register contains 1234H, and the IP register contains 5678H, then the next instruction is fetched from physical address 179B8H, which is 1234H times 16 (12340H) plus 5678H. The segment register used is selected by context, or by using a segment override prefix, however, the code segment register (CS) can not be overidden during instruction fetch, nor can the stack segment register (SS) be overidden during stack pushes and pops.
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
What is defference between direct and indirect address?
The I bit is 0 so the instruction is recognice as a direct address instruction The indirect address instruction needs 2 referance to memory to fetch & opened The I bit is 1 so the instruction is recognice as a indirect address instructionhe
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 instruction buffer register?
An instruction buffer register is a component of a computer's central processing unit (CPU) that temporarily stores instructions fetched from memory before they are decoded and executed. It acts as a staging area for instructions, allowing the CPU to quickly access and process them in the correct order. The instruction buffer register helps improve overall system performance by reducing the time it takes for the CPU to retrieve and execute instructions.
How an instruction is executed in sap-1?
In SAP-1 (Simple Asynchronous Processor), instruction execution involves a series of steps. First, the instruction is fetched from memory using the Program Counter (PC), which points to the address of the next instruction. The fetched instruction is then decoded to determine the operation and the operands involved. Finally, the execution phase carries out the operation, which may involve reading from or writing to memory, updating registers, or performing arithmetic operations. This cycle is repeated for each instruction until the program completes.
