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Explain instruction fetch and execution with a state diagram?
Instruction fetch and execution are key phases in a CPU's operation cycle. In the state diagram, the process begins in the "Fetch" state, where the CPU retrieves an instruction from memory using the Program Counter (PC) to locate it. Next, the CPU transitions to the "Decode" state to interpret the instruction, followed by the "Execute" state where the instruction is carried out. After execution, the CPU may return to the "Fetch" state to retrieve the next instruction, creating a continuous loop that forms the basis of program execution.
What happens when halt instruction is executed?
The processor stops and goes to the halt state. If an interrupt occurs, it responds and then continues execution.
Why is RET is an emulated instruction but RETI is not?
RET (return from subroutine) is an emulated instruction because its execution involves handling the return address and potentially changing the CPU state or context, which can vary based on different execution environments. In contrast, RETI (return from interrupt) is not emulated because it is directly supported by the hardware, allowing it to efficiently restore the previous execution state and enable interrupts, ensuring that the system can handle interrupts quickly and reliably. The distinction lies in the complexity and requirements of returning from different types of calls or states.
What are various types of operations required for instruction Explain each?
Instruction execution in a computer involves several key operations: Fetch: The CPU retrieves an instruction from memory, using the program counter to determine the address of the next instruction. Decode: The fetched instruction is then interpreted by the control unit to determine the required action and the operands involved. Execute: The actual operation (arithmetic, logic, or control) is performed by the ALU (Arithmetic Logic Unit) or other processing units. Write-back: The results of the execution are written back to memory or registers, updating the system's state for subsequent instructions.
What instruction is HLT?
HLT, or Halt, is an assembly language instruction used to stop the execution of a program. When the CPU encounters the HLT instruction, it enters a low-power state until an interrupt occurs, effectively pausing operations. This instruction is commonly used at the end of a program or to signal that the CPU should wait for further instructions. In some systems, it helps manage power consumption and resource allocation.
What does PUSHAD instruction accomplish?
The PUSHAD instruction in x86 assembly language pushes the values of all general-purpose registers (EAX, EBX, ECX, EDX, ESI, EDI, EBP, and ESP) onto the stack in a specific order. This is useful for saving the state of the registers before performing operations that might modify them, allowing for easy restoration later. Upon execution, it decreases the stack pointer (ESP) accordingly to accommodate the pushed values. This instruction is primarily used in procedures where preserving the register state is necessary.
How many T state required for excution of POP instruction?
The execution of the POP instruction typically requires 5 T-states. This includes the time needed for fetching the instruction, reading the stack pointer, accessing the memory location of the data to be popped, updating the stack pointer, and finally storing the data into the specified register or memory location. The exact timing may vary slightly depending on the specific architecture being referenced.
What do you mean by wait state?
A wait state in computing refers to a condition where a microprocessor is held idle until it can proceed with the execution of the next instruction. This can occur due to various reasons, such as unavailability of data or resources needed to complete the current operation. Efficient management of wait states is crucial for optimizing processor performance.
What states have the highest execution rates?
the state is texas
What is minimum and maximum marriage age between a girl and a boy?
The minimum varies from state to state. The maximum is "until death". (There is no maximum age listed, in any state.)
If the clock frequency is 5 MHz how much time is required to execute an instruction of 18 T states?
At a clock frequency of 5 MHz (10 MHz crystal) the 8085 has a clock period of 200 ns. An instruction using 18 cycles would use 3.6 us. (Microseconds)This is for the case with no wait states. Each wait state adds 200 ns. Since an 18 cycle instruction has 5 memory accesses, one wait state per access would add 1 us to the execution time.
If clock frequency is 5 MHz how much time is required to execute an instruction of 18 T states?
At a clock frequency of 5 MHz (10 MHz crystal) the 8085 has a clock period of 200 ns. An instruction using 18 cycles would use 3.6 us. (Microseconds)This is for the case with no wait states. Each wait state adds 200 ns. Since an 18 cycle instruction has 5 memory accesses, one wait state per access would add 1 us to the execution time.
