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Posted: **Tue Apr 22, 2008 9:37 am**

Hello,

I am currently working on the hardware interrupts, so I must remap the PIC .
I've read JamesM's tutorial but he dont describe clearly ( In other words : I'm dumb

) how to remap the PIC... After I've searched on Google, I've found some descriptions about the PIC, but I'm still not sure if my PIC remap function is correct, here's the code :

Code: Select all

void remap_pic(){
	outb(0x20, 0x11);
	io_wait();
	outb(0xA0, 0x11);
	io_wait();
	outb(0x21, 0x20);
	io_wait();
	outb(0xA1, 0x70);
	io_wait();
	outb(0x21, 0x04);
	io_wait();
	outb(0xA1, 0x02);
	io_wait();
	outb(0x21, 0x01);
	io_wait();
	outb(0xA1, 0x01);
	io_wait();
	outb(0x21, inb(0x21) && 0xFC);
	io_wait();
	outb(0xA1, 0xFF);
}

I want to use IRQ0 ( clock ) and IRQ1 ( keyboard ), so I have to use AND like this : " inb(0x21) && 0xFC " ( 0xFC = 11111100 ), Is that correct ?

Thanks .

Posted: **Tue Apr 22, 2008 4:28 pm**

I'll point you here which describes the format of the operational command words used by the pic as well as other details.

When remapping the pic, you are only giving it the base interrupt handlers for it to use within your IDT. Everything else is almost automatic. It is your responsibility to insure the interfaces set up and install there interrupt handlers in the IDT.

For example, the timer is always irq 0 as it is connected to the pic's ir0 line. Because of this, once you give the pic the base interrupt numbers in your IDT to use, you are done with the PIC.

Assuming that you remap the primary PIC to use int 0x20, just install the timers interrupt handler to int 0x20 and enable hardware interrupts (sti).

Posted: **Wed Apr 23, 2008 4:43 am**

Thanks neon, I understand more now and I've succesfully handled the timer and keyboard interrupts on my OS

PS : thanks for the link

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PIC remapping

PIC remapping