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Altera_Forum's avatar
Altera_Forum
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20 years ago

interrupt duration

I wonder, how long I have to set an interrupt. For one clock cycle, until there is some response, ... Has anyone a clue?
Altera_Forum's avatar
Altera_Forum
Icon for Honored Contributor rankHonored Contributor
20 years ago

You must keep your interrupt signal asserted until it is cleared by a software action.

Most hardware uses a write to a bit in a register to clear the interrupt, but some (for example the UART read interrupt) uses a read from a particular register (which can be faster but is harder to debug).

If you deassert the interrupt line before software has had a chance to deal with it then you have sent what is known as a "spurious interrupt".

The HAL software will spin in the interrupt handler when it gets a spurious interrupt to make it obvious that your system is broken (its easier to debug synchronisation problems if the bug always happens rather than just one time in 100).