What happens when an interrupt is raised & before ISR is executed?
When a device raises an interrupt at let’s say process i, the processor first completes the execution of instruction i. Then it loads the Program Counter (PC) with the address of the first instruction of the ISR. This is called Interrupt Latency.
What happens during an interrupt?
When an interrupt occurs, it causes the CPU to stop executing the current program. The control then passes to a special piece of code called an Interrupt Handler or Interrupt Service Routine. The interrupt handler will process the interrupt and resume the interrupted program.
What is ISR in microprocessor?
Stands for “Interrupt Service Routine.” An ISR (also called an interrupt handler) is a software process invoked by an interrupt request from a hardware device. It handles the request and sends it to the CPU, interrupting the active process. Without an interrupt request, a computer will remain in its current state.
What happens when ISR is called?
Like the reset vector, the C18 compiler does not automatically start the ISR at the high or low interrupt vector in program memory.
How does an ISR work?
An interrupt service routine (ISR) is a software routine that hardware invokes in response to an interrupt. ISR examines an interrupt and determines how to handle it executes the handling, and then returns a logical interrupt value. If no further handling is required the ISR notifies the kernel with a return value.
Is the last instruction of ISR?
The last instruction of the ISR is RETI, which causes the microcontroller to pick up running where it left off before the interrupt happened. The microcontroller goes back to the MOV instruction, since it’s after the SUB instruction that was running when the interrupt happened.
Is an interrupt an instruction?
Interrupt instructions include EXIT, SIGNAL, CALL, and RETURN. Instructions that interrupt the flow of a program can cause the program to: Go temporarily to a subroutine either within the program or outside the program (CALL or RETURN). …
What is ISR in 8051?
The most powerful and important features are interrupts in 8051 microcontroller. Interrupt Service Routine (ISR) comes into the picture when interrupt occurs, and then tells the processor to take appropriate action for the interrupt, and after ISR execution, the controller jumps into the main program.