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ds:si packet address int 13h ah=42h
Posted: Sun May 13, 2012 4:04 pm
by Mikemk
Sorry if the answer is obvious, but how would one put the address of the ds:si packet in ds:si using nasm?
Re: ds:si packet address int 13h ah=42h
Posted: Sun May 13, 2012 6:09 pm
by evoex
Read up on segmentation and real-mode on the wiki:
http://wiki.osdev.org/Segmentation
http://wiki.osdev.org/Real_Mode
Hope that helps
Re: ds:si packet address int 13h ah=42h
Posted: Sun May 13, 2012 8:09 pm
by Mikemk
evoex wrote:http://wiki.osdev.org/Segmentation
Thanks, quite helpful
Re: ds:si packet address int 13h ah=42h
Posted: Sun May 13, 2012 8:25 pm
by Mikemk
Code: Select all
1 mov [si], DWORD [packet]
2 mov es:[bx], 0x500
line 1 produces "error: operation size not specified"
line 2 produces "error: invalid combination of opcode and operands"
What am I doing wrong?
Re: ds:si packet address int 13h ah=42h
Posted: Sun May 13, 2012 8:45 pm
by Mikemk
nm, I figured it out
Re: ds:si packet address int 13h ah=42h
Posted: Mon May 14, 2012 1:29 pm
by neon
nm, I figured it out
Im not convinced you have....
mov [es:bx], ax stores ax into the location at es:bx; it does not set es nor bx. If you want to set ds and si to contain the address of the packet, you need to know real mode addressing:
Code: Select all
mov ax, 0x7c0 ; ds:si -> 0x7c0:packet
mov ds, ax
mov si, packet