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initial loader prototype, needs hex conversion

This commit is contained in:
Jeremiah Orians 2016-05-17 22:41:19 -04:00
parent dddb80af94
commit 01af3b6d5f
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1 changed files with 69 additions and 0 deletions
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stage1_loader.s Normal file
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BITS 16
;; Steps for building
;; nasm -o stage1_loader stage1_loader.s
;;
;; Steps for testing
;; qemu -fda stage1_loader
;; Then insert another program to load and run
start:
;; Wait for user input before running
mov ah, 00h
int 16h
;; Clear the screen to be nice
;; Routine: clears the display
mov al, 0 ; Clear screen
mov ah, 06h ; Scroll up
mov bh, 07h ; Move Color
mov cl, 0 ; UL x coordinate
mov ch, 0 ; UL y coordinate
mov dl, 80 ; LR x coordinate
mov dh, 24 ; LR y coordinate
int 10h
;; Routine: reset the cursor
mov ah, 02h ; Set cursor position
mov bh, 0 ; Set Page number to 0
mov dh, 0 ; Set Row Number
mov dl, 0 ; Set Column Number
int 10h
read_floppy:
;; Read bytes from floppy
mov al, 128 ; Number of sectors to read
mov ah, 02h ; Read sectors to memory
mov ch, 0 ; Cylinder Number
mov cl, 1 ; Starting sector number
mov dh, 0 ; Drive head number
mov dl, 00h ; Drive number [floppy A:]
mov bx, 01000h ; Starting segment
mov es, bx ; Loaded into the required segment register
mov bx, 0 ; At the exact start of the segment
int 13h ; Make the function call
jc read_floppy
;; Zero all registers and segments before jump
mov ax, 0
mov bx, 0
mov cx, 0
mov dx, 0
mov si, 0
mov di, 0
mov bp, 0
mov ds, ax
mov ss, ax
mov es, ax
mov fs, ax
mov gs, ax
;; Load the code that we input by hand
push 01000h
push 0h
;; Using intersegment return
iret
done:
hlt
times 510-($-$$) db 90h ; Pad remainder of boot sector with NOPs
dw 0xAA55 ; The standard PC boot signature