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[/] [eco32/] [trunk/] [simtest/] [disk/] [mkmbr/] [mbr.s] - Blame information for rev 79

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Line No. Rev Author Line
1 9 hellwig
;
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; mbr.s -- the master boot record
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;
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; $8  I/O base address
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; $9  temporary value
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; $10 character
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; $11 pointer to string
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; $29 stack pointer
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; $31 return address
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        .set    tba,0xF0300000  ; terminal base address
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start:
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        sub     $29,$29,4       ; save return register
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        stw     $31,$29,0
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        add     $8,$0,tba        ; set I/O base address
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        add     $11,$0,msg       ; pointer to string
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loop:
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        ldbu    $10,$11,0        ; get char
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        beq     $10,$0,stop      ; null - finished
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        jal     out             ; output char
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        add     $11,$11,1       ; bump pointer
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        j       loop            ; next char
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stop:
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        ldw     $31,$29,0        ; restore return register
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        add     $29,$29,4
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        jr      $31             ; return
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out:
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        ldw     $9,$8,8         ; get status
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        and     $9,$9,1         ; xmtr ready?
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        beq     $9,$0,out        ; no - wait
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        stw     $10,$8,12       ; send char
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        jr      $31             ; return
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msg:
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        .byte   0x0D, 0x0A
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        .byte   "Error: This is the default MBR, "
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        .byte   "which cannot load anything."
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        .byte   0x0D, 0x0A
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        .byte   "Please replace the disk, or "
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        .byte   "write an operating system onto it."
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        .byte   0x0D, 0x0A
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        .byte   0x0D, 0x0A, 0
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        .locate 512-2
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sign:
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        .byte   0x55, 0xAA

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