Questions about "interrupt"

Question

Could someone help me clarify the following conecpts, and the relationship among them?

• Maskable interrupt
• Unmaskable interrupt
• Hardware interrupt
• Software interrupt
• CPU INTR pin
• the IF bit of EFlags register

Some specific questions:

• What's the relationship between Maskable/Unmaskable interrupt and Hardware/Software interrupt?
• What's the relationship between maskability and being software/hardware?
• Is there any unmaskable/software interrupt and maskable/hardware interrupt?
• What kind of interrupts does INTR pin detect?
• What kind of interrupts are enabled/disabled by IF bit of EFlags register?
• What kind of interrupts need the presence of an interrupt controller?

Many thanks.

Answer 1

Interrupts

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Maskable: Can be enabled/disabled by setting the proper bit.

• Non-Maskable: Can NOT be enabled/disabled. (no designated bit).

• Hardware: RST, INTR etc. Whenevr the h/w pin is activated properly h/w INTERRUPT occurs.

• Software: An Interrupt raised by using the INTERRUPT software instruction.

• INTR pin is Interrupt receive pin.

• All interrupts are handled by the "Interrupt-handler" i.e. Interrupt service routine (ISR). An ISR is a function written, that is executed when an interrupt occurs.

• IF (bit 9) Interrupt enable flag : Controls the response of the processor to maskable interrupt requests. Set to respond/enable to maskable interrupts; cleared to inhibit/disable maskable interrupts.

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A lot more Q & A info here:

• http://www.techinterviews.com/8086-interview-questions

For a detailed explanation. Plz refer the book Microprocessor x86 by Barry B Brey

GoodLuck!!