54 lines
1.0 KiB
NASM
54 lines
1.0 KiB
NASM
; drive table
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%define drivetab_type 0x00 ; BYTE 0=unassigned, 1=BIOS/CHS, 2=BIOS/LBA
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%define drivetab_num 0x01 ; BYTE DL number
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; CHS data for type=1
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; Might be reused for driver address
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%define drivetab_heads 0x02 ; WORD CHS heads
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%define drivetab_spt 0x04 ; WORD CHS sectors per track
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%define drivetab_sectors 0x06 ; DWORD total number of sectors
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%define drivetab_offset 0x0A ; DWORD partition offset
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%define drivetab_size 0x0E
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drive_table:
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dw 0
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.count:
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dw 4
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; DI is incremented for the space taken
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; IN ES:DI
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drive_setup:
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xor cx, cx
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mov [drive_table], di
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mov al, drivetab_size
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mov ah, BYTE [drive_table.count]
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mul ah
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xchg cx, ax
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; this increments DI and also fills table with zeros
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rep stosb
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ret
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; Load a drive table entry
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; IN DL drive number
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; OUT DS:SI ptr to table item
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drive_load:
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; bail out if number too high
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cmp dl, [cs:drive_table.count]
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jnc .err
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push cs
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pop ds
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mov si, [drive_table]
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push ax
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mov al, drivetab_size
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mul dl
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add si, ax
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pop ax
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ret
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.err:
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stc
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ret
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