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What happens if the ISR is supposed to clear the interrupt flag and it didn t?
If you don’t clear the flag, and the hardware doesn’t clear the flag (this occurs for some flags but not all) then as soon as the interrupt ends the interrupt controller will see the interrupt flag and fire the ISR again.
Are interrupts disabled during ISR?
An interrupt should be generally cleared the moment you enter ISR. If it’s not cleared, the hardware keeps interrupting the CPU and the safety code inside ISR will never execute.
Can an ISR be interrupted?
Normally, an interrupt service routine proceeds until it is complete without being interrupted itself in most of the systems. However, If we have a larger system, where several devices may interrupt the microprocessor, a priority problem may arise.
What does ISR stand for interrupt?
In computer systems programming, an interrupt handler, also known as an interrupt service routine or ISR, is a special block of code associated with a specific interrupt condition.
What happens if there is an interrupt when any interrupt routine is being served?
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 happens when an interrupt is generated?
When an interrupt occurs, it causes the CPU to stop executing the current program. When it is generated, the processor saves its execution state via a context switch, and begins executing the interrupt handler at the interrupt vector.
How are interrupts served?
Each interrupt signal is associated with a bit in the mask register; on some systems, the interrupt is enabled when the bit is set and disabled when the bit is clear, while on others, a set bit disables the interrupt. When the interrupt is disabled, the associated interrupt signal will be ignored by the processor.
When to re-enable interrupts in an ISR-blogger?
At that point the ISR can re-enable interrupts if it wants to, or leave them masked until the ISR completes execution. (The “return from interrupt” instruction will typically restore interrupt flags, re-enabling interrupts as appropriate when the ISR completes.)
What should the basepri be to enable interrupts?
For example if the software sets the BASEPRI to 3, then requests with level 0, 1, and 2 can interrupt, while requests at levels 3 and higher will be postponed. The software can also specify the priority level of each interrupt request. If BASEPRI is zero, then the priority feature is disabled and all interrupts are allowed.
What does it mean to enable or disable interrupts?
One arms a trigger if one is interested in interrupts from this source. Conversely, one disarms a trigger if one is not interested in interrupts from this source. To enable means to allow interrupts at this time. Conversely, to disable means to postpone interrupts until a later time.
What do you need to know about interrupt programming?
Study the basics of interrupt programming: arm, enable, trigger, vector, priority, acknowledge. Use SysTick to create sounds and spin motors. If playback doesn’t begin shortly, try restarting your device.