OSDev.org

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begin:
mov sp,stackstart
push cs; THANKS TROY!
pop ds
push cs
pop es    ;done setting segments
mov BYTE[drive],dl     ; store the boot drive
;;;;;;;;;;;;;;;Load next 3 Sectors To complete stage1;;;;;;;;;;;;;;;;;;
mov ah,0x08
mov dl,BYTE [drive] 
int 0x13        ; get drive parameters
jc FAIL     ;did this faiL?
;else store info for LBA TO CHS

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mov BYTE [HPC], dh ;//store heads per cylinder 

mov ax,0 ;; start counter for all the bits

testandset: ; tests and sets all the sector bits in cl
bt cx,ax     ; test bit
jc set       ; is the bit set? if yes set it in SPT
inc ax    ; if no go to next bit and test set
cmp ax,6
je continue ;if we are finished, continue with the rest of  the code
jmp testandset


set:
bts WORD [SPT],ax
inc ax
cmp ax,6
je continue ;if done setting, continue
jmp testandset ;we are not done

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PUSH CS
POP DS
MOV ES,DS

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[john@john-arch ~]$ yasm -f bin test.s
test.s:5: error: invalid combination of opcode and operands

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MOV AX, CS
MOV DS, AX
MOV ES, AX