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mmekh
Beginner
911 Views

Does BIOS in Atom-32bit-intel board make IDT and GDT?

I have Atom-32bit-intel board n450 with only BIOS in it, my goal is to use APIC timer and linke it with an ISR (0x21). After a while, I discoverd that IDT and GDT already exist(probably built by the BIOS) and no need to build them (the software is in C language and AT&T assembly):

/*Read the IDTR*/ sidt (idt_ptr) /*Read the GDTR*/ sgdt (gdt_ptr)

So I tried just to use IDT's address to link my ISR to the IDT :

fill_interrupt(ISR_Nbr,(unsigned int) isr33, 0x08, 0x8E); static void fill_interrupt(unsigned char num, unsigned int base, unsigned short sel, unsigned char flags) { unsigned short *Interrupt_Address; /*address = idt_ptr.base + num * 8 byte*/ Interrupt_Address = (unsigned short *)(idt_ptr.base + num*8); *(Interrupt_Address) = base&0xFFFF; *(Interrupt_Address+1) = sel; *(Interrupt_Address+1) = (flags>>8)&0xFF00; *(Interrupt_Address+1) = (base>>16)&0xFFFF; }

When I try to call the ISR33 : int $0x21, the software crashes : SingleStep CPU[1] Error : Processor Running.

So where is it wrong ???

Remark: I use eclipse Heros(AT&T assembly), the code is in protected mode (CR0.PE = 1 I checked it, probably set by the BIOS).

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FMcNu1
Valued Contributor I
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Hello and Welcome to the Intel® Embedded Community.

I want to make you aware of a special place to go with questions like yours. The Intel® e-Help desk is staffed by Intel representatives who support select Intel embedded platforms including Atom

To access e-Help, you need to be a Privileged member of the Intel® Embedded Community. If you are not already a Privileged member, you can request an upgrade to your community account here:

https://edc.intel.com/My-Account.aspx https://edc.intel.com/My-Account.aspx

In addition to access to e-Help, Prvileged members may also access the confidential content within the Intel® Embedded Design Center, such as design documents, specifications, and training materials.

I hope this helps.

Felix

J. Felix McNulty

Community Moderator (Intel contractor)

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