75 lines
907 B
NASM
75 lines
907 B
NASM
cpu 8086
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; Memory layout (starting from top)
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%define self 0xF000
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; A single sector for disk i/o
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%define diskbuf (self-0x200)
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; DWORD partition offset for C: and D:
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%define parttab (diskbuf - (2*4))
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%define stack (parttab)
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%define default_drive BYTE [0x5B]
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%define fcb_size 31
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org self
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jmp init
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banner:
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db "RDOS 2019-09", 0x0A, 0x0D, 0
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print_banner:
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mov cl, 2
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mov si, banner
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.loop:
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mov dl, BYTE [si]
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test dl, dl
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jz .end
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call cpm_syscall
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inc si
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jmp .loop
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.end:
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ret
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init:
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mov sp, stack
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call print_banner
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mov si, init_program
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call exec
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cli
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.halt:
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hlt
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jmp .halt
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init_program:
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db "HELLO.COM", 0
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cpm_syscall:
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cmp cl, 0x02
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je putc
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stc
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ret
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putc:
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push ax
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push bx
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mov al, dl
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mov ah, 0x0e
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mov bx, 0x0000
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int 0x10
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pop bx
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pop ax
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ret
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%include "exec.asm"
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%include "fcb.asm"
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%include "fcbparse.asm"
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%include "drive.asm"
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%include "log2.asm"
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