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Erik Malund
01/17/12 10:21
Read: 371 times
Mt Airy, Nc

#185538 - what you think does not cause interrupts
Responding to: Shankara Rao's previous message
many misunderstandings re '51 interrupts come from the belief that things directly cause nterrupts, they do not.

neither the UART nor the SPI causes an interrupt. Both just set an "interrupt request flag".

Then when the processor is ready (done with current instruction, not interrupts higher or current priority running) it will check the flags and decide if/which interrupt to take.

thus for a shared interrupt: when coming out of the interrupt it will check the flags so if e.g. the SPI flag get set during asn UART interrupt, the SPI interrupt will then be executed.


List of 4 messages in thread
Shared interrupts.      Shankara Rao      01/17/12 10:10      
   what you think does not cause interrupts      Erik Malund      01/17/12 10:21      
   You will not lose anything.      David Prentice      01/17/12 10:25      
      no surprise      Erik Malund      01/17/12 10:46      

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