irq.htm

mips架构的bootloader,99左右的版本 但源代码现在没人更新了

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<title>The IRQInstall Library Function</title>
<h1 align=center>The IRQInstall Library Function</h1>

<!--INDEX "Installing C exception handlers" IRQInstall -->

</dl><h2>NAME</h2><dl><dd>
     IRQInstall - connect C exception handler

</dl><h2>SYNOPSIS</h2><dl><dd>
<pre>
Func *IRQInstall(int IRQNum, Func *ISRFun)
</pre>

</dl><h2>DESCRIPTION</h2><dl><dd>
     IRQInstall connects a C language exception handler to  a
     selected  EXCCODE  in  the CAUSE register.
     It returns the address of previous C function that was
     installed for this exception. <p>

     If the IRQNum is 0..7, the appropriate mask bit in the Status
     register will be enabled, together with the global IEC bit.<p>


     IRQNum (0..23) specifies which of the possible 24 exceptions vectors
     should be connected to this handler.<p>

     <center>
     <table border=1><tr>
     <th>IRQNum</th><th>Exception</th>
       <th>IRQNum</th><th>Exception</th></tr><tr>
     <td align=right>0</td><td>	- sw0	(low priority)</td>
       <td align=right>12</td><td> - AdEL</td></tr><tr>
     <td align=right>1</td><td>	- sw1</td>
       <td align=right>13</td><td> - AdES</td></tr><tr>
     <td align=right>2</td><td>	- int0</td>
       <td align=right>14</td><td> - IBE</td></tr><tr>
     <td align=right>3</td><td>	- int1</td>
       <td align=right>15</td><td> - DBE</td></tr><tr>
     <td align=right>4</td><td>	- int2</td>
       <td align=right>16</td><td> - Sys</td></tr><tr>
     <td align=right>5</td><td>	- int3</td>
       <td align=right>17</td><td> - Bp</td></tr><tr>
     <td align=right>6</td><td>	- int4</td>
       <td align=right>18</td><td> - RI</td></tr><tr>
     <td align=right>7</td><td>	- int5 (high priority)</td>
       <td align=right>19</td><td> - CpU</td></tr><tr>
     <td align=right>8</td><td>	- unused</td>
       <td align=right>20</td><td> - Ovf</td></tr><tr>
     <td align=right>9</td><td>	- TLB MOD</td>
       <td align=right>21</td><td> - unused</td></tr><tr>
     <td align=right>10</td><td> - TLBL</td>
       <td align=right>22</td><td> - unused</td></tr><tr>
     <td align=right>11</td><td> - TLBS</td>
       <td align=right>23</td><td> - unused</td></tr><tr>

	</table> </center><p>

     ISRFun is the address of the C function that should be called
     when the specified exception occurs. If a value of zero is specified,
the current handler will be uninstalled and the interrupt will be disabled.<p>

     The ISRFun is passed the base address of the register save area, this
     permits the ISR to receive incoming register-based variables, and even
     change the address to which control will pass when the handler 
	terminates.<p>

      Offsets in the savearea are 0 thru 31 where the offset equals the
     register number except for the following cases:<p>

<pre>
                0 = EPC
               26 = HI
               27 = LO
               28 = CAUSE
               29 = SR
</pre>

     The ISRFun <b>must</b> return non-zero if it handled the exception.
     If it returns zero, control will be passed to the ICEKernel or
     PMON.<p>

     There are actually two separate implementations of this command,
     <a href="../../lib/pmirq.c">lib/pmirq.c</a> and 
     <a href="../../lib/sairq.c">lib/sairq.c</a>.
     When you build a program for execution under PMON, your 
     reference to IRQInstall will pull 
     <a href="../../lib/irq.c">lib/irq.c</a> from the library. This
     module then calls pmirq.c. It is different from sairq.c in
     that it uses <a href="onintr.htm">onintr</a> to add the 
     handler to PMON's interrupt vector table.  <p>


</dl><h2>EXAMPLE</h2><dl><dd>

<pre>
main()
{
int isr();

IRQInstall(SIO_IRQNum,isr);
}
 
isr(Ulong *savearea)
{
/* acknowledge the interrupt */
/* do interrupt code */
return(1);
}
</pre><p>

For more complete examples, see 
<a href="../../lib/p2681.c">lib/p2681.c</a> and
<a href="../../lib/t1_4102.c">lib/t1_4102.c</a>.<p>

</dl><p><hr>
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