ipl.nas

; hello-os
; TAB=4

CYLS    EQU 10

    ORG 0x7c00

; For FAT12 Format FloppyDisk

    JMP entry
    DB  0x90
    DB  "BOOTNAME"
    DW  512
    DB  1
    DW  1
    DB  2
    DW  224
    DW  2880
    DB  0xf0
    DW  9
    DW  18
    DW  2
    DD  0
    DD  2880
    DB  0, 0, 0x29
    DD  0xffffffff
    DB  "HELLO-OS   "
    DB  "FAT12   "
    RESB    18

; 本体

entry:
    MOV AX, 0
    MOV SS, AX
    MOV SP, 0x7c00
    MOV DS, AX
    
; read disk
	MOV AX, 0x0820
    MOV ES, AX
    MOV CH, 0       ; シリンダー0
    MOV DH, 0       ; Head 0
    MOV CL, 2       ; Sector2

readloop:
    MOV SI, 0       ; 失敗回数用

retry:
    MOV AH, 0x02    ; read disk
    MOV AL, 1
    MOV BX, 0
    MOV DL, 0x00
    INT 0x13
    JNC next
    ADD SI, 1
    CMP SI, 5
    JAE error
    MOV AH, 0x00
    MOV DL, 0x00
    INT 0x13        ; reset drive
    JMP retry
next:
    MOV AX,ES
    ADD AX, 0x0020  ; 512/16
    MOV ES, AX
    ADD CL, 1
    CMP CL, 18
    JBE readloop
    MOV CL, 1
    ADD DH, 1
    CMP DH, 2
    JB  readloop
    MOV DH, 0
    ADD CH, 1
    CMP CH, CYLS
    JB  readloop

; exexute haribote.sys 
    MOV [0x0ff0], CH    ; IPLが読み込んだCYLS数をメモ
    JMP 0xc200

fin:
    HLT
    JMP fin

error:
    MOV SI, msg

putloop:
    MOV AL, [SI]
    ADD SI, 1
    CMP AL, 0
    JE  fin
    MOV AH, 0x0e
    MOV BX, 15
    INT 0x10
    JMP putloop

msg:
    DB  0x0a, 0x0a
    DB  "load error"
    DB  0x0a
    DB  0

    RESB    0x7dfe-$

    DB  0x55, 0xaa