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What is priority mechanism of interrupts?
A priority interrupt is a system which decides the priority at which various devices, which generates the interrupt signal at the same time, will be serviced by the CPU. When two or more devices interrupt the computer simultaneously, the computer services the device with the higher priority first.
Which device used for setting the priority of interrupts?
Hence, the device having PI = 1 and PO = 0 is the highest priority device that is requesting an interrupt. Therefore, by daisy chain arrangement we have ensured that the highest priority interrupt gets serviced first and have established a hierarchy.
What are the methods to handle interrupt from multiple devices?
Handling Multiple Devices: When more than one device raises an interrupt request signal, then additional information is needed to decide which device to be considered first. The following methods are used to decide which device to select: Polling, Vectored Interrupts, and Interrupt Nesting.
Which is the highest priority interrupt among interrupts given below?
Explanation: The interrupt, IE0(External INT0) is given the highest priority among all the interrupts.
What’s the difference between Lower and higher priority interrupts?
In summary, higher priority interrupt can “interrupt” the execution of lower priority ISR any time (known as preemption in nested interrupts), while lower priority cannot preempt higher priority ISR. It can only wait or remain “pending”.
How is the priority of interrupts determined in daisy chaining?
The daisy-chaining method involves connecting all the devices that can request an interrupt in a serial manner. This configuration is governed by the priority of the devices. The device with the highest priority is placed first followed by the second highest priority device and so on. The given figure depicts this arrangement.
Which is the device with the highest priority?
The device having the highest priority is checked first and then devices are checked in descending order of priority. If the device is checked to be generating the interrupt, another service program is called which works specifically for that particular device. The major disadvantage of this method is that it is quite slow.
When does an interrupt occur what should be done?
Interrupts are just signals coming from external circuit and hence can occur at any time. ISR is the task that should be performed by the controller when an interrupt occurs. Whenever an interrupt occurs, corresponding interrupt flag is set. And the corresponding ISR is executed.