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I Can't Get Interrupts Working: Difference between revisions
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Use the mask feature of the PIC to enable/disable some handlers.
<source lang="c">
outb(0x21,0xfd);
outb(0xa1,0xff);
enable(); // asm("sti");
</
=== I'm receiving EXC9 instead of IRQ1 when striking a key ?! ===
Line 55:
=== I can only receive one IRQ ===
Each IRQ needs to be acknowledged to the PIC manually. You need to have <
=== When I try to enable the PIT, the keyboard doesn't work anymore ===
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=== I keep getting an IRQ7 for no apparent reason ===
This is a known problem that cannot be prevented from happening, although there is a workaround. When any IRQ7 is received, simply read the In-Service Register <
For more information, including a more detailed explanation, see Brendan's post in [[Topic:11379|this thread]].
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You're trying to load a 16-bits field (a part of the IDT descriptor) with a reference to a 32-bit label that is subject to relocation. Try to replace
<source lang="asm">
isr_label:
iret
Line 80:
dw 0xbeef
dw isr_label >> 16
</source>
by something that extracts a 'pure value' from the address (e.g. the difference of two addresses are a pure value and <tt>$$</tt> means to NASM the start of the section)
<source lang="asm">
%define BASE_OF_SECTION SOME_CONSTANT_YOU_SHOULD_KNOW
isr_label:
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dw 0xbabe
dw (BASE_OF_SECTION isr_label - $$) >> 16
</source>
The role of <pre>BASE_OF_SECTION</pre> is to adjust the pure offset to the real situation (usually as defined in your linker script), e.g. if your kernel get loaded at 1MB, you'll set it to 0x100000 to keep the CPU happy.
==Assembly Example==
<source lang="asm">
int_handler:
mov ax, LINEAR_DATA_SELECTOR
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mov [idt+49*8+6],ax
int 49
</source>
should display a smiley on the top-left corner ... then the CPU is halted indefinitely.
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simple, but not like Nasm.
a little example, so you can see how it works:
<source lang="asm">
idt:
dw ((isr1 shl 0x30) shr 0x30) ; the low part of the address
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db 010001110b ; type
dw (isr1 shr 0x10) the high part of the address
isr1:
mov ax,0xdead
</source>
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