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IRQ is disalbed, but ISR is called, Why?

Altera_Forum
Honored Contributor II
‎04-05-2013 03:55 PM
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HI, 

 

UART is interrupt driven. When IRQ for the UART is asserted, its ISR is called. In the ISR, after it reads buffer, it raises an Event. A separate Thread waiting at the Event activated when the Event is posted. In the Thread, it disables IRQ for the Uart. Then it does further processing. I expected that next IRQ will not be served until its IRQ is re-enabled again. But it seems to me that, the ISR has been called during the IRQ is disabled. Can anyone help me explain why? 

 

Thank you, 

David
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