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    10 <!DOCTYPE concept

    11   PUBLIC "-//OASIS//DTD DITA Concept//EN" "concept.dtd">

    12 <concept id="GUID-660A8E4C-F930-415C-8CCC-CB1DCCAA2442" xml:lang="en"><title>Interrupts</title><shortdesc>This document describes how device drivers use interrupts.</shortdesc><prolog><metadata><keywords/></metadata></prolog><conbody>

    13 <section id="GUID-7B450286-637E-4BAB-9D36-9228764CD0D4">      

    14       <p>Devices generate interrupts to indicate hardware events. Generally

    15 drivers provide an interrupt service routine (ISR) to handle the interrupts

    16 and perform the required responses to the events. Symbian provides an <xref href="GUID-E7A7083C-97B9-39B9-A147-4A6E314EE3A3.dita"><apiname>Interrupt</apiname></xref> class

    17 (implemented by the ASSP) with an API to bind and unbind an interrupt source

    18 and an ISR. </p> <codeblock id="GUID-9EB4BFFE-55A2-56D4-BCF3-6D278C3EC4F4" xml:space="preserve">// Bind the interrupt source ID and interrupt service routine

    19 TInt Bind(TInt aId, TIsr aIsr, TAny* aPtr);

    20 // Unbind the interrupt

    21 TInt Unbind(TInt aId);

    22 // Enable interrupts on device interrupt source

    23 TInt Enable(TInt aId);

    24 // Disable interrupts on device interrupt source

    25 TInt Disable(TInt aId);

    26 // Clear the device interrupt

    27 TInt Clear(TInt aId);

    28 // Set the priority of the interrupt

    29 TInt SetPriority(TInt aId, TInt aPriority);</codeblock> <p>Interrupt handling

    30 is typically done in a PDD, as device hardware access is done at that level.

    31 Interrupt handling is generally done in two stages in the driver. High priority

    32 and short time running tasks are done in the ISR, and the remaining processing

    33 is deferred for handling later. </p> <p>Interrupt handling is a blocking high

    34 priority task and needs to take a minimal amount of time. The Kernel will

    35 be in an indeterminate state and puts restrictions on doing various operations. </p> 

    36    </section>

    37 </conbody></concept>