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boot.S
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697 lines (640 loc) · 11.1 KB
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/*
* "BOOT" ROM
*/
.globl _start
.text
.mri 1
IDEBASE equ $00F01000
MMUMASK equ $00F02000
MMUROOT equ $00F02010
MMUFAULT equ $00F02020
SERIN equ $00F03000
SEROUT equ $00F03000
SERSTAT equ $00F03010
TIMERIO equ $00F04000
MMUIRQ equ 7
TIMERIRQ equ 6
; Vectors at address 0
; Boot vectors (0,1)
long $00000ffe ; Boot SP
long boot ; Boot PC
; System exceptions (2-15)
long bomb ; Bus error
long bomb ; Address error
long bomb ; Illegal
long bomb ; Div 0 (int)
long bomb ; CHK/CHK2
long bomb ; TRAPcc/TRAPV
long bombp ; Privilege violation
long bomb ; Trace trap
long bomb ; A line
long bomb ; F line
long bomb ; unused
long bomb ; unused (no coprocessor on a 68000)
long bomb ; unused (format on 68010+)
long bomb ; uninitialized interrupt vector
; Reserved (16-23)
long bomb ; spare 16
long bomb ; spare 17
long bomb ; spare 18
long bomb ; spare 19
long bomb ; spare 20
long bomb ; spare 21
long bomb ; spare 22
long bomb ; spare 23
; Spurious IRQ (24)
long bomb ; spare 24
; Autovector IRQ (25-31)
long ignore ; Level 1
long ignore ; Level 2
long ignore ; Level 3
long ignore ; Level 4
long ignore ; Level 5
long timer ; Level 6
long ignore ; Level 7
; Traps (32-47)
long bomb ; Trap 0
long bomb ; Trap 1
long bomb ; Trap 2
long bomb ; Trap 3
long bomb ; Trap 4
long bomb ; Trap 5
long bomb ; Trap 6
long bomb ; Trap 7
long bomb ; Trap 8
long bomb ; Trap 9
long bomb ; Trap 10
long bomb ; Trap 11
long bomb ; Trap 12
long bomb ; Trap 13
long bomb ; Trap 14
long bomb ; Trap 15
; FPU 48-55(unused)
long bomb ; BSUC
long bomb ; Inexact
long bomb ; Div0
long bomb ; Underflow
long bomb ; Operand error
long bomb ; Overflow
long bomb ; NaN
long bomb ; Unimplemented data (68040+)
; MMU 56-58 (unused - not on 68000)
long bomb ; Configuration error
long bomb ; Illegal operation
long bomb ; Access level violation
; Reserved (59-63)
long bomb
long bomb
long bomb
long bomb
long bomb
; User vectors 64-255
long bomb ; 64
long bomb
long bomb
long bomb
long bomb
long bomb
long bomb
long bomb
long bomb ; 72
long bomb
long bomb
long bomb
long bomb
long bomb
long bomb
long bomb
long bomb ; 80
long bomb
long bomb
long bomb
long bomb
long bomb
long bomb
long bomb
long bomb ; 88
long bomb
long bomb
long bomb
long bomb
long bomb
long bomb
long bomb
long bomb ; 96
long bomb
long bomb
long bomb
long bomb
long bomb
long bomb
long bomb
long bomb ; 104
long bomb
long bomb
long bomb
long bomb
long bomb
long bomb
long bomb
long bomb ; 112
long bomb
long bomb
long bomb
long bomb
long bomb
long bomb
long bomb
long bomb ; 120
long bomb
long bomb
long bomb
long bomb
long bomb
long bomb
long bomb
long bomb ; 128
long bomb
long bomb
long bomb
long bomb
long bomb
long bomb
long bomb
long bomb ; 136
long bomb
long bomb
long bomb
long bomb
long bomb
long bomb
long bomb
long bomb ; 144
long bomb
long bomb
long bomb
long bomb
long bomb
long bomb
long bomb
long bomb ; 152
long bomb
long bomb
long bomb
long bomb
long bomb
long bomb
long bomb
long bomb ; 160
long bomb
long bomb
long bomb
long bomb
long bomb
long bomb
long bomb
long bomb ; 168
long bomb
long bomb
long bomb
long bomb
long bomb
long bomb
long bomb
long bomb ; 176
long bomb
long bomb
long bomb
long bomb
long bomb
long bomb
long bomb
long bomb ; 184
long bomb
long bomb
long bomb
long bomb
long bomb
long bomb
long bomb
long bomb ; 192
long bomb
long bomb
long bomb
long bomb
long bomb
long bomb
long bomb
long bomb ; 200
long bomb
long bomb
long bomb
long bomb
long bomb
long bomb
long bomb
long bomb ; 208
long bomb
long bomb
long bomb
long bomb
long bomb
long bomb
long bomb
long bomb ; 216
long bomb
long bomb
long bomb
long bomb
long bomb
long bomb
long bomb
long bomb ; 224
long bomb
long bomb
long bomb
long bomb
long bomb
long bomb
long bomb
long bomb ; 232
long bomb
long bomb
long bomb
long bomb
long bomb
long bomb
long bomb
long bomb ; 240
long bomb
long bomb
long bomb
long bomb
long bomb
long bomb
long bomb
long bomb ; 248
long bomb
long bomb
long bomb
long bomb
long bomb
long bomb
long bomb
; End of vector table (Address $0400)
_start:
boot:
; Print a first letter so the world knows we got this far
move.l #SEROUT,a0
move.b #'V',(a0)
move.l #banner,a3
bsr strout
; Size memory
move.l #$1000,a1
moveq #0,d1
sizeit: clr.l (a1)
move.l 0,d0
tst.l (a1)+ ; it will go FFFFFFFF when we go off
beq sizeit ; the end
; interrupts on for timers
and.w #$F8FF,sr
move.l #namehd0,a3
moveq #0,d0
bsr identify_drive
moveq #1,d0
move.l #namehd1,a3
bsr identify_drive
command:
move.l #prompt,a3
bsr strout
move.l #$7000,a2
moveq #80,d2
bsr strin
move.b $7000,d0
beq command
cmp.b #'b',d0
beq cmd_boot
cmp.b #'r',d0
beq cmd_reset
move.l #badcmd,a3
bsr strout
bra command
;
; Identify the drive in D0, on entry A3 is the drive name
;
identify_drive:
move.l d0,-(sp)
bsr strout
move.l (sp)+,d0
; Set up a 30 second timeout exception
move.l #command,a0
move.l a0,-(sp)
move.l sp,timeoutsp
move.w #3000,d1
move.w d1,ticktock
move.l #$1000,a0
bsr diskidentify
clr.w ticktock ; stop timeouts
tst.w d0
beq identok
move.l (sp)+,a2
move.l #notfound,a3
bra strout
identok:
move.l (sp)+,a2 ; throw away timeout return
move.l #$1036,a2 ; ident string
moveq #19,d2 ; 40 byte space padded
ideident:
move.b 1(a2),d0
bsr chrout
move.b (a2),d0
bsr chrout
addq #2,a2
dbra d2,ideident
bsr newline
rts
cmd_boot:
;
; Now try and load the boot block from IDE
;
move.l #ideload,a3
bsr strout
; Set up a 30 second timeout exception
move.l #command,a0
move.l a0,-(sp)
move.l sp,timeoutsp
move.w #3000,d1
move.w d1,ticktock
move.l #$1000,a0 ; Store data at $1000
clr.l d0 ; Disk 0
clr.l d1 ; Block 0
bsr diskload
move.l (sp)+,a0
tst.w d0
beq boottime
move.l #diskfault,a3
bsr strout
boottime:
; And run it - there is much to flesh out in the boot ROM
; yet !
move.l $1000,d0
cmp.l #$15C0DE68,d0
beq bootit
move.l #notboot,a3
bsr strout
bra halt
bootit:
clr.b TIMERIO
move.l #gogogo,a3
bsr strout
move.l #bootservices,a6
moveq #0,d0 ; D0 = disk we booted from
or.w #$0700,sr ; IRQ off
jmp $1004 ; Entered with A6 as service vector
; Trap or fault taken
bombp:
move.l #priv,a3
bra bombs
bomb:
move.l #unexpected,a3
bombs: bsr strout
halt: move.l #$0ffe,sp
move.l #hitkey,a3
bsr strout
bsr chrin
cmd_reset:
move.l #$8000,sp
reset
bra boot
ignore: rte
timer:
move.w d0,-(sp)
cmp.b TIMERIO,d0 ; clear irq without using a register
move.w ticktock,d0
beq tickon
sub.w #1,d0
beq ticktickboom
move.w d0,ticktock
tickon:
move.w (sp)+,d0
rte
;
; Return from the trap to our recovery routine
;
ticktickboom:
move.w (sp)+,d0
clr.w (sp)
move.l #bang,2(sp)
rte
bang:
clr.w ticktock
move.l timeoutsp,a7
move.l #timeout,a3
bsr strout
rts
;
; Library Routines
; Trash input registers and A0/D0/A1/D1
;
;
; Print zero terminated string in A3
;
strout:
move.l #SEROUT,a0
move.b (a3)+,d0
tst.b d0
beq strend
strw1: btst #1,10(a0)
beq strw1
move.b d0,(a0)
bra strout
strend: rts
newline:
move.b #13,d0
bsr chrout
move.b #10,d0
;
; Print character in D0
;
chrout:
move.l #SEROUT,a0
chrw1: btst #1,10(a0)
beq chrw1
move.b d0,(a0)
rts
;
; Read a character into D0
;
chrin:
move.l #SERIN,a0
chrr1: btst #0,10(a0)
beq chrr1
move.b (a0),d0
and.b #$7F,d0
rts
;
; Check input status
;
; Bit 0 = read ready bit 1 = write ready
;
chrpoll: move.b SERIN,d0
and.b #3,d0
rts
;
; Read a line of input
;
; A2 = buffer, D2.w = length of buffer
;
strin: move.l a3,-(sp)
move.l a2,a3
subq #1,d2 ; reserve space for CR
strinl: bsr chrin
cmp.b #8,d0
beq strdel
cmp.b #127,d0
beq strdel
cmp.b #10,d0
beq strent
cmp.b #32,d0
blt strinl
tst.w d2
beq strinl
move.b d0,(a2)+
bsr chrout
subq #1,d2
bra strinl
strdel: cmpa a2,a3
beq strinl
move.b #8,d0
bsr chrout
move.b #' ',d0
bsr chrout
move.b #8,d0
bsr chrout
addq #1,d2
sub.l #1,a2
bra strinl
strent: bsr newline
clr.b (a2)
move.l (sp)+,a3
rts
;
; Load block D1 from disk D0 (currently disk must be 0/1) into A0
;
; FIXME: needs timeouts
;
; Returns D0 = 0 on success, non zero on error
;
diskload:
move.l d0,-(sp)
bsr idenotbusy
move.l (sp)+,d0
tst.w d0
beq disk0sel
cmp.w #1,d0
bne diskerr ; No such drive
move.b #$F0,d0 ; Disk select bit
bra disk1sel
disk0sel:
move.b #$E0,d0
disk1sel:
move.b d0,13(a1) ; drive 0 E0 / drive 1 F0
move.b d0,-(sp)
bsr ideready
move.b (sp)+,d0
move.b d1,7(a1) ; disk block n (assumes LBA)
ror.l #8,d1
move.b d1,9(a1)
ror.l #8,d1
move.b d1,11(a1)
ror.l #8,d1
and.b #$0F,d1
or.b d0,d1
move.b #1,5(a1) ; for one sector only
move.b #$20,15(a1) ; read sector
diskwait3: ; Wait for DRQ
btst #0,15(a1) ; Error bit ?
bne diskerr
btst #3,15(a1) ; DRQ
beq diskwait3
move.w #255,d0
diskblk: move.w (a1),d1 ; Copy the bytes
move.w d1,(a0)+
; move.l #SEROUT,a5
; move.b #'D',(a5)
dbra d0,diskblk
moveq #0,d0
rts
diskerr: moveq #1,d0
rts
idenotbusy: move.l #IDEBASE,a1
move.w #20000,d2
idewait1:
btst #7,15(a1) ; Wait for drive to come ready
beq idewait_over
sub.w #1,d2
bne idewait1
idewait_over: rts
ideready: ; Wait for ready
move.w #20000,d2
ideready_l:
btst #0,15(a1) ; Error bit ?
bne diskerr
btst #6,15(a1)
bne idewait_over
sub.w #1,d2
bne ideready_l
rts
;
; Identify disk D0 (currently disk must be 0/1) into A0
;
; FIXME: needs timeouts
;
; Returns D0 = 0 on success, non zero on error
;
diskidentify: bsr idenotbusy
tst.w d2
beq selfail
moveq #0,d1
tst.w d0
beq diski0sel
cmp.w #1,d0
bne diskerr ; No such drive
or.b #$10,d1 ; Disk select bit
diski0sel:
or.b #$E0,d1
move.b d1,13(a1) ; drive 0 E0 / drive 1 F0
bsr ideready
tst.w d2
beq selfail
move.b #$EC,15(a1) ; identify
bra diskwait3 ; transfer as if a sector
selfail:
moveq #1,d0
rts
;
; Expose our minimal services to the code we boot
;
bootservices: jmp halt
jmp chrout
jmp strout
jmp chrin
jmp chrpoll
jmp strin
jmp diskload
ticktock: word 0
timeoutsp long 0
banner: asciz "68 Boot Services\r\nRevision 0.1 Alpha\r\n\r\nClearing memory\r\n"
ideload: asciz "Booting from IDE disk 0\r\n"
gogogo: asciz "OK\r\n"
notboot: asciz "Not a bootable device\r\n"
unexpected: asciz "Unexpected trap: halting\r\n"
priv: asciz "Privilege violation\r\n"
diskfault: asciz "Disk error\r\n"
hitkey: asciz "Hit a key to restart\r\n"
prompt: asciz "> "
badcmd: asciz "Unknown command\r\n"
timeout: asciz "Timed out\r\n"
namehd0: asciz "ide0: "
namehd1: asciz "ide1: "
notfound: asciz "not present\r\n"