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What is the difference between interrupt Raw status register and interrupt status register on LPC3250?
If you refer to the LPC32x0 user manual chapter #5 it states for the Raw Status Register:
... RSR shows which interrupt sources are active before being masked by the ER.
whereas it states for the Interrupt status Register:
... Status Registers provide information on which interrupts are actually pending, after being masked by the corresponding Enable Register
Is there something wrong with your copy of the user manual?
yes. i got this point from user manual. but my question is are we need to check this register before enable interrupt on ER register. Is this make any difference if we won't check? For interrupt on GPIO i used RSR interrupt to acknowledge. but in timer we have TnIR to acknoledge. how can we use this registar?
The normal approach would be to fully initialise the source of the interrupt before enabling the interrupt. That initialisation would clear (release) any old pending interrupt.
Thank you. i got the difference.