61 lines
737 B
NASM
61 lines
737 B
NASM
cpu 8086
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org 0x0
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jmp init
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isr_dos_main:
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cmp ah, 0x01
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je isr_getc_echo
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cmp ah, 0x02
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je isr_putc
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cmp ah, 0x25
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je isr_intr_register
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jmp isr_invalid
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%include "intr.asm"
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%include "chario.asm"
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; ISR for invalid subfunctions or unimplemented
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isr_invalid:
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mov bp, 0xFEFE
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int3
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.hlt:
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hlt
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jmp .hlt
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; ISR tail to set carry flag to signal error
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isr_error:
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push bp
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mov bp, sp
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; set carry flag
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or WORD [SS:BP+6], 1
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pop bp
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isr_return:
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iret
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%include "drive.asm"
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init:
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mov ax, cs
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mov ds, ax
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mov es, ax
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mov di, kernel_end
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call drive_setup
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mov dx, isr_dos_main
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mov ax, 0x2521
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pushf
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push cs
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call isr_dos_main
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mov dl, 0x37
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mov ah, 0x02
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int 0x21
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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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kernel_end:
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