When an interrupt occurs, the address following the current instruction is stored on the stack.
When the 8086 microprocessor receives an interrupt signal, it completes the execution of the current instruction and saves the address of the next instruction onto the stack. It then determines the appropriate interrupt vector from the Interrupt Vector Table (IVT) based on the interrupt type. The processor then transfers control to the interrupt service routine (ISR) associated with that interrupt. After the ISR has executed, the 8086 retrieves the saved address from the stack and resumes execution from where it was interrupted.
Finishes the current executing instruction and then serves the interrupt.
In the 8086 microprocessor, the register that stores the interrupt and subroutine return address is the Instruction Pointer (IP) register. When an interrupt occurs or a subroutine is called, the current instruction address is pushed onto the stack, allowing the processor to return to that location after the interrupt or subroutine execution is complete. The IP register works in conjunction with the Code Segment (CS) register to determine the effective address of the next instruction to execute.
when interrupt occurs, the program counter content will stores into stack, an PC will load interrupt address for next instruction execution. ofter completion ISR process PC will retrieves the stack values and execution will be continued.
when this interrupt occurs, the processor fetches the bus one instruction usually one of these instructions as given, one of the 8 RST instructions( RST0 - RST7), the processor saves the current program counter into the stack and the branches from N*8 (where N is 3 bit number from 0 to 7). call instruction which is a 3 byte inst. the first byte is the address branch which chosen based on the second and the third byte of the instruction set.
the following steps are required to invoke a rom-bios function 1)make an interrupt to occur 2)find out the number of the interrupt that has occurred. 3)obtain from IVT,the address of the ISR which services this interrupt. 4)push the current values of CPU register onto the STACK
Processor serves the interrupt request after completing the execution of the current instruction.
Yes, the "Current PSW" contains machine state and next instruction address. It is a 64 bit register, and bits 33-63 (AMODE=31) or bits 40-63 (AMODE=24) contain the address of the next instruction to be executed. Certain "restartable" instructions, while in flight, will maintain the current instruction address until the sequence is complete, and certain exceptions, "early exceptions", will contain the current instruction address but, in general, the PSW (33-63) contains the address of the next instruction to execute.
program counter holds the address of the next instruction.
Branch Instruction A branch (or jump on some computer architectures, such as the PDP-8 and Intel x86) is a point in a computer program where the flow of control is altered. The term branch is usually used when referring to a program written in machine code or assembly language; in a high-level programming language, branches usually take the form of conditional statements, subroutine calls or GOTO statements. An instruction that causes a branch, a branch instruction, can be taken or not taken: if a branch is not taken, the flow of control is unchanged and the next instruction to be executed is the instruction immediately following the current instruction in memory; if taken, the next instruction to be executed is an instruction at some other place in memory. There are two usual forms of branch instruction: a conditional branch that can be either taken or not taken, depending on a condition such as a CPU flag, and an unconditional branch which is always taken. Call Subroutine instructions Call Subroutine instructions and Return From Subroutine instructions within the instruction stream. The first stage stores a return address in a return register when a Call Subroutine instruction is predicted. The first stage predicts a return to the return address in the return register when a Return From Subroutine instruction is predicted. A second stage decodes each Call Subroutine and Return From Subroutine instruction in order to maintain a Return Stack Buffer that stores a stack of return addresses. Each time the second stage decodes a Call Subroutine instruction, a return address is pushed onto the Return Stack Buffer. Correspondingly, each time the second stage decodes a Return From Subroutine instruction, a return address is popped off of the Return Stack Buffer. The second stage verifies predictions made by the first stage and predicts return addresses for Return From Subroutine instructions that were not predicted by the first stage. A third stage executes Return From Subroutine instructions such that the predictions are verified. Finally, a fourth stage retires Return From Subroutine instructions and ensures that no instructions fetch after a mispredicted return address are committed into permanent state. Program interrupt an interrupt is an asynchronous signal from hardware indicating the need for attention or a synchronous event in software indicating the need for a change in execution. A hardware interrupt causes the processor to save its state of execution via a context switch, and begin execution of an interrupt handler. Software interrupts are usually implemented as instructions in the instruction set, which cause a context switch to an interrupt handler similar to a hardware interrupt. Interrupts are a commonly used technique for computer multitasking, especially in real-time computing. Such a system is said to be interrupt-driven. An act of interrupting is referred to as an interrupt request ("IRQ").
When an interrupt is pending, the processor will temporarily halt its current execution to address the interrupt signal. It saves the state of the current process, including the program counter and registers, to ensure that it can resume later. The processor then jumps to the interrupt service routine (ISR) associated with the interrupt to handle the specific event. Once the ISR completes, the processor restores the saved state and resumes the interrupted process.
The address of the current instruction in the control unit is held by a register called the Program Counter (PC). The PC keeps track of the memory location of the next instruction to be executed in a program. As each instruction is fetched and executed, the PC is incremented to point to the subsequent instruction. This allows the control unit to manage the flow of execution in a sequential manner.