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The Interrupt flag (IF) is a flag bit in the processor’s FLAGS register, which determines whether or not the central processing unit (CPU) will respond immediately to maskable hardware interrupts.
How do you set an interrupt flag?
STI — Set Interrupt Flag STI sets the interrupt flag to 1. The 80386 then responds to external interrupts after executing the next instruction if the next instruction allows the interrupt flag to remain enabled.
Which flag bit is set to 1 in case of an interrupt?
Interrupt Flag (I) – This flag is for interrupts. If interrupt flag is set (1), the microprocessor will recognize interrupt requests from the peripherals. If interrupt flag is reset (0), the microprocessor will not recognize any interrupt requests and will ignore them.
What is the bit of the interrupt flag?
The bit, which is bit 9 of the FLAGS register, may be set or cleared by programs with sufficient privileges, as usually determined by the operating system. If the flag is set to 1, maskable hardware interrupts will be handled. If cleared (set to 0 ), such interrupts will be ignored.
Why do interrupt flags exist on a microchip?
This allows the hardware to set the interrupt again if needed. If you wait until the end of the interrupt you risk ignoring another case of the condition firing.
How does executing CLI affect the interrupt flag?
Note that CLI only affects the interrupt flag for the processor on which it is executed; in multiprocessor systems, executing a CLI instruction does not disable interrupts on other processors. Thus, a driver/interrupt handler race condition can still occur because other processors may service interrupts and execute the offending interrupt handler.
How does the global interrupt enable bit work?
The way interrupts work: The code sets the “Global Interrupt Enable” bit; without it, no interrupts will occur. When something happens to cause an interrupt, a flag is set. When the interrupt flag is noticed, the “Global Interrupt Enable” bit is cleared.