From e5c28a46a731a79d02266aa690a90a8f809d0f70 Mon Sep 17 00:00:00 2001
From: kotorifan <kotorifan05@gmail.com>
Date: Sat, 31 Jan 2026 15:22:00 +0100
Subject: A20 enable code added

---
 src/boot/boot.stage1.asm | 64 ++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 64 insertions(+)
 create mode 100644 src/boot/boot.stage1.asm

(limited to 'src/boot/boot.stage1.asm')

diff --git a/src/boot/boot.stage1.asm b/src/boot/boot.stage1.asm
new file mode 100644
index 0000000..801860e
--- /dev/null
+++ b/src/boot/boot.stage1.asm
@@ -0,0 +1,64 @@
+    ;; boot.stage1.asm
+
+    %include "boot.common.asm"
+    %include "boot.stage1.print.asm"
+    [org 0x7c00]    
+    [bits 16]
+
+    %define READ_SECTORS_NUM 64
+    %define BOOT_LOAD_ADDR 0x7c00
+    %define SECTOR_SIZE 512
+
+    global _start
+
+_start: 
+    ;; Disable interrupts
+    cli                         
+
+    ;; Setup segment registers
+    xor ax, ax
+    mov ds, ax
+    mov es, ax  
+    mov ss, ax
+
+    ;; Adjust Stack
+    mov sp, _start
+    
+    clc
+
+    mov si, disk_addr_packet
+    mov ah, 0x42                ; BIOS extended read function
+    mov dl, 0x80                ; Drive number
+    int 0x13                    ; BIOS disk services
+    jc _disk_read_err
+    
+    mov si, disk_read_success_msg
+    call _print_string
+
+    jmp 0x0000:0x7e00
+
+_disk_read_err: 
+    mov si, disk_read_err_msg
+    call _print_string
+
+    hlt
+    jmp _disk_read_err
+
+_end:
+    hlt 
+    jmp _end
+
+disk_read_err_msg: db "Failed to read disk", 13, 10, 0
+disk_read_success_msg: db "Read the disk successfully", 13, 10, 0
+disk_addr_packet:  
+    db 0x10
+    db 0x00
+    dw READ_SECTORS_NUM
+    dw 0x0000
+    dw 0x7e00
+    dq 1
+
+    ;; Padding and magic number
+    times 510 - ($ - $$) db 0
+    dw 0xaa55
+    
-- 
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