| Line 2... |
Line 2... |
; mbr.s -- the master boot record
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; mbr.s -- the master boot record
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;
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;
|
|
|
; Runtime environment:
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; Runtime environment:
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;
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;
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; This code must be loaded and started at 0xC0000000.
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; This code must be loaded and started at 0xC0010000.
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; It allocates a stack from 0xC0001000 downwards. So
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; It allocates a stack from 0xC0011000 downwards. So
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; it must run within 4K (code + data + stack).
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; it must run within 4K (code + data + stack).
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;
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;
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; This code expects the disk number of the boot disk
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; This code expects the disk number of the boot disk
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; in $16, the start sector of the disk or partition
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; in $16, the start sector of the disk or partition
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; to be booted in $17 and its size in $18.
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; to be booted in $17 and its size in $18.
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;
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;
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; The boot manager, which is loaded by this code,
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; The boot manager, which is loaded by this code,
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; must be in standalone (headerless) executable
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; must be in standalone (headerless) executable
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; format, stored at absolute disk sectors 2..31,
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; format, stored at absolute disk sectors 2..31,
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; and gets loaded and started at 0xC0001000.
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; and gets loaded and started at 0xC0011000.
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|
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.set stacktop,0xC0001000 ; top of stack
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.set stacktop,0xC0011000 ; top of stack
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.set loadaddr,0xC0001000 ; where to load the boot manager
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.set loadaddr,0xC0011000 ; where to load the boot manager
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|
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.set cout,0xE0000018 ; ROM console output
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.set cout,0xC0000018 ; the monitor's console output
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.set dskio,0xE0000030 ; ROM disk I/O
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.set dskio,0xC0000030 ; the monitor's disk I/O
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|
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; reset arrives here
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reset:
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j start
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|
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; interrupts arrive here
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intrpt:
|
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j userMiss
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; user TLB misses arrive here
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userMiss:
|
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add $4,$0,intmsg ; we do not expect any interrupt
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jal msgout
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j halt
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|
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; load the boot manager and start it
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; load the boot manager and start it
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start:
|
start:
|
add $29,$0,stacktop ; setup stack
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add $29,$0,stacktop ; setup stack
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add $4,$0,strtmsg ; say what is going on
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add $4,$0,strtmsg ; say what is going on
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| Line 111... |
Line 97... |
jal msgout
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jal msgout
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halt1:
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halt1:
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j halt1
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j halt1
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; messages
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; messages
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intmsg:
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.byte "unexpected interrupt", 0x0D, 0x0A, 0
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strtmsg:
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strtmsg:
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.byte "MBR executing...", 0x0D, 0x0A, 0
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.byte "MBR executing...", 0x0D, 0x0A, 0
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dremsg:
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dremsg:
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.byte "disk read error", 0x0D, 0x0A, 0
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.byte "disk read error", 0x0D, 0x0A, 0
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hltmsg:
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hltmsg:
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