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I believe a nested interrupt, is where an interrupt is allowed to occur (and thus is handled) during an already occurring Interupt service ruotine.


First interrupt occurs

ISR1 begins

second Interrupt occurs

ISR2 begins

ISR2 Finishes

ISR1 continues from where left off

ISR1 finishes

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โˆ™ 2011-09-13 17:12:37
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Q: What is nested interrupt?
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Related questions

Should any device be allowed to interrupt CPU while another interrupts are being serviced?

It is possible to allow nested interrupts. This is often done when there is a heirarchy of interrupts, some with higher priority than others. In order for this to work, the second interrupt must not be allowed to influence the progress of the first interrupt. We call this being "thread safe". In a nested scheme, an interrupt mask is set so that higher priority interrupts can be permitted, while blocking interrupts of the same or lower priority, and then interrupts are reenabled during the interrupt service routine. At the conclusion of the first routine, interrupts are disabled again, the mask is restored, and the normal interrupt return sequence is executed. In the 8085, this can be supported using the Read Interrupt Mask (RIM) and Set Interrupt Mask (SIM) instructions. While not strictly required, the logical priority is often INTR, RST5.5, RST6.6, RST7.5, and then TRAP, in order of increasing priority.

Why there is a need for disabling interrupts in 8085?

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That is the correct spelling: interrupt.

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the prefix of interrupt is in