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cc65/libsrc/cbm510/crt0.s
cuz 467d8ad9c5 Added routines to handle command line params 
git-svn-id: svn://svn.cc65.org/cc65/trunk@2012 b7a2c559-68d2-44c3-8de9-860c34a00d81
2003-03-10 21:21:46 +00:00

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11 KiB
ArmAsm
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;
; Startup code for cc65 (CBM 500 version)
;
; This must be the *first* file on the linker command line
;
.export _exit
.import _clrscr, initlib, donelib
.import push0, callmain
.import __CHARRAM_START__, __CHARRAM_SIZE__, __VIDRAM_START__
.import __EXTZP_RUN__, __EXTZP_SIZE__
.import __BSS_RUN__, __BSS_SIZE__
.import irq, nmi
.import k_irq, k_nmi, PLOT, UDTIM, SCNKEY
.include "zeropage.inc"
.include "extzp.inc"
.include "cbm510.inc"
; ------------------------------------------------------------------------
; BASIC header and a small BASIC program. Since it is not possible to start
; programs in other banks using SYS, the BASIC program will write a small
; machine code program into memory at $100 and start that machine code
; program. The machine code program will then start the machine language
; code in bank 0, which will initialize the system by copying stuff from
; the system bank, and start the application.
;
; Here's the basic program that's in the following lines:
;
; 10 for i=0 to 4
; 20 read j
; 30 poke 256+i,j
; 40 next i
; 50 sys 256
; 60 data 120,169,0,133,0
;
; The machine program in the data lines is:
;
; sei
; lda #$00
; sta $00 <-- Switch to bank 0 after this command
;
; Initialization is not only complex because of the jumping from one bank
; into another. but also because we want to save memory, and because of
; this, we will use the system memory ($00-$3FF) for initialization stuff
; that is overwritten later.
;
.code
; To make things more simple, make the code of this module absolute.
.org $0001
Head: .byte $03,$00,$11,$00,$0a,$00,$81,$20,$49,$b2,$30,$20,$a4,$20,$34,$00
.byte $19,$00,$14,$00,$87,$20,$4a,$00,$27,$00,$1e,$00,$97,$20,$32,$35
.byte $36,$aa,$49,$2c,$4a,$00,$2f,$00,$28,$00,$82,$20,$49,$00,$39,$00
.byte $32,$00,$9e,$20,$32,$35,$36,$00,$4f,$00,$3c,$00,$83,$20,$31,$32
.byte $30,$2c,$31,$36,$39,$2c,$30,$2c,$31,$33,$33,$2c,$30,$00,$00,$00
; The code in the target bank when switching back will be put at the bottom
; of the stack. We will jump here to switch segments. The range $F2..$FF is
; not used by any kernal routine.
.res $F8-*
Back: ldx spsave
txs
lda IndReg
sta ExecReg
; The following code is a copy of the code that is poked in the system bank
; memory by the basic header program, it's only for documentation and not
; actually used here:
sei
lda #$00
sta ExecReg
; This is the actual starting point of our code after switching banks for
; startup. Beware: The following code will get overwritten as soon as we
; use the stack (since it's in page 1)!
tsx
stx spsave ; Save the system stackpointer
ldx #$FF
txs ; Set up our own stack
; Set the interrupt, NMI and other vectors
ldy #vectable_size
L0: lda vectable-1,y
sta $FF81-1,y
dey
bne L0
; Initialize the extended zero page variables
ldx #zptable_size
L1: lda zptable-1,x
sta <(__EXTZP_RUN__-1),x
dex
bne L1
; Switch the indirect segment to the system bank
lda #$0F
sta IndReg
; Copy the kernal zero page ($90-$F2) from the system bank
lda #$90
sta ptr1
lda #$00
sta ptr1+1
ldy #$62-1
L2: lda (ptr1),y
sta $90,y
dey
bpl L2
; Copy the page 3 vectors in place
ldy #$00
L3: lda p3vectable,y
sta $300,y
iny
cpy #p3vectable_size
bne L3
; Copy the rest of page 3 from the system bank
lda #$00
sta ptr1
lda #$03
sta ptr1+1
L4: lda (ptr1),y
sta $300,y
iny
bne L4
; Set the indirect segment to bank we're executing in
lda ExecReg
sta IndReg
; Zero the BSS segment. We will do that here instead calling the routine
; in the common library, since we have the memory anyway, and this way,
; it's reused later.
lda #<__BSS_RUN__
sta ptr1
lda #>__BSS_RUN__
sta ptr1+1
lda #0
tay
; Clear full pages
ldx #>__BSS_SIZE__
beq Z2
Z1: sta (ptr1),y
iny
bne Z1
inc ptr1+1 ; Next page
dex
bne Z1
; Clear the remaining page
Z2: ldx #<__BSS_SIZE__
beq Z4
Z3: sta (ptr1),y
iny
dex
bne Z3
Z4:
; Setup the C stack
lda #<$FF81
sta sp
lda #>$FF81
sta sp+1
; We expect to be in page 2 now
.if (* < $1FD)
jmp $200
.res $200-*
.endif
.if (* < $200)
.res $200-*,$EA
.endif
.if (* >= $2F0)
.error "Code range invalid"
.endif
; This code is in page 2, so we may now start calling subroutines safely,
; since the code we execute is no longer in the stack page.
; Copy the character rom from the system bank into the execution bank
lda #<$C000
sta ptr1
lda #>$C000
sta ptr1+1
lda #<__CHARRAM_START__
sta ptr2
lda #>__CHARRAM_START__
sta ptr2+1
lda #>__CHARRAM_SIZE__ ; 16 * 256 bytes to copy
sta tmp1
ldy #$00
ccopy: lda #$0F
sta IndReg ; Access the system bank
ccopy1: lda (ptr1),y
sta __VIDRAM_START__,y
iny
bne ccopy1
lda ExecReg
sta IndReg
ccopy2: lda __VIDRAM_START__,y
sta (ptr2),y
iny
bne ccopy2
inc ptr1+1
inc ptr2+1 ; Bump high pointer bytes
dec tmp1
bne ccopy
; Clear the video memory. We will do this before switching the video to bank 0
; to avoid garbage when doing so.
jsr _clrscr
; Reprogram the VIC so that the text screen and the character ROM is in the
; execution bank. This is done in three steps:
lda #$0F ; We need access to the system bank
sta IndReg
; Place the VIC video RAM into bank 0
; CA (STATVID) = 0
; CB (VICDOTSEL) = 0
ldy #tpiCtrlReg
lda (tpi1),y
sta vidsave+0
and #%00001111
ora #%10100000
sta (tpi1),y
; Set bit 14/15 of the VIC address range to the high bits of __VIDRAM_START__
; PC6/PC7 (VICBANKSEL 0/1) = 11
ldy #tpiPortC
lda (tpi2),y
sta vidsave+1
and #$3F
ora #<((>__VIDRAM_START__) & $C0)
sta (tpi2),y
; Set the VIC base address register to the addresses of the video and
; character RAM.
ldy #VIC_VIDEO_ADR
lda (vic),y
sta vidsave+2
and #$01
ora #<(((__VIDRAM_START__ >> 6) & $F0) | ((__CHARRAM_START__ >> 10) & $0E) | $02)
; and #$0F
; ora #<(((>__VIDRAM_START__) << 2) & $F0)
sta (vic),y
; Switch back to the execution bank
lda ExecReg
sta IndReg
; Call module constructors
jsr initlib
; Execute the program code
jmp Start
; ------------------------------------------------------------------------
; Additional data that we need for initialization and that's overwritten
; later
zptable:
.word $d800 ; vic
.word $da00 ; sid
.word $db00 ; cia1
.word $dc00 ; cia2
.word $dd00 ; acia
.word $de00 ; tpi1
.word $df00 ; tpi2
.word $eab1 ; ktab1
.word $eb11 ; ktab2
.word $eb71 ; ktab3
.word $ebd1 ; ktab4
.dword $0000 ; time
.word $0100 ; RecvBuf
.word $0200 ; SendBuf
zptable_size = * - zptable
vectable:
jmp $0000 ; CINT
jmp $0000 ; IOINIT
jmp $0000 ; RAMTAS
jmp $0000 ; RESTOR
jmp $0000 ; VECTOR
jmp $0000 ; SETMSG
jmp $0000 ; SECOND
jmp $0000 ; TKSA
jmp $0000 ; MEMTOP
jmp $0000 ; MEMBOT
jmp SCNKEY
jmp $0000 ; SETTMO
jmp $0000 ; ACPTR
jmp $0000 ; CIOUT
jmp $0000 ; UNTLK
jmp $0000 ; UNLSN
jmp $0000 ; LISTEN
jmp $0000 ; TALK
jmp $0000 ; READST
jmp SETLFS
jmp SETNAM
jmp $0000 ; OPEN
jmp $0000 ; CLOSE
jmp $0000 ; CHKIN
jmp $0000 ; CKOUT
jmp $0000 ; CLRCH
jmp $0000 ; BASIN
jmp $0000 ; BSOUT
jmp $0000 ; LOAD
jmp $0000 ; SAVE
jmp SETTIM
jmp RDTIM
jmp $0000 ; STOP
jmp $0000 ; GETIN
jmp $0000 ; CLALL
jmp UDTIM
jmp SCREEN
jmp PLOT
jmp IOBASE
sta ExecReg
rts
.byte $01 ; Filler
.word nmi
.word 0 ; Reset - not used
.word irq
vectable_size = * - vectable
p3vectable:
.word k_irq ; IRQ user vector
.word k_brk ; BRK user vector
.word k_nmi ; NMI user vector
p3vectable_size = * - p3vectable
; ------------------------------------------------------------------------
; This is the program code after setup. It starts at $400
.res $400-*
Start:
; Enable interrupts
cli
; Push arguments and call main()
jsr callmain
; Call module destructors. This is also the _exit entry.
_exit: jsr donelib ; Run module destructors
; We need access to the system bank now
lda #$0F
sta IndReg
; Switch back the video to the system bank
ldy #tpiCtrlReg
lda vidsave+0
sta (tpi1),y
ldy #tpiPortC
lda vidsave+1
sta (tpi2),y
ldy #VIC_VIDEO_ADR
lda vidsave+2
sta (vic),y
; Clear the start of the zero page, since it will be interpreted as a
; (garbage) BASIC program otherwise. This is also the default entry for
; the break vector.
k_brk: sei
lda #$00
ldx #$3E
Clear: sta $02,x
dex
bne Clear
; Setup the welcome code at the stack bottom in the system bank. Use
; the F4/F5 vector to access the system bank
ldy #$00
sty $F4
iny
sty $F5
ldy #reset_size-1
@L1: lda reset,y
sta ($F4),y
dey
bne @L1
jmp Back
; ------------------------------------------------------------------------
; Code that is copied into the system bank at $100 when switching back
reset: cli
jmp $8000 ; BASIC cold start
reset_size = * - reset
; ------------------------------------------------------------------------
; Code for a few simpler kernal calls goes here
.export IOBASE
.proc IOBASE
ldx cia2
ldy cia2+1
rts
.endproc
.export SCREEN
.proc SCREEN
ldx #40 ; Columns
ldy #25 ; Lines
rts
.endproc
.export SETLFS
.proc SETLFS
sta LogicalAdr
stx FirstAdr
sty SecondAdr
rts
.endproc
.export SETNAM
.proc SETNAM
sta FileNameLen
lda $00,x
sta FileNameAdrLo
lda $01,x
sta FileNameAdrHi
lda $02,x
sta FileNameAdrSeg
rts
.endproc
.export RDTIM
.proc RDTIM
sei
lda time+0
ldx time+1
ldy time+2
cli
rts
.endproc
.export SETTIM
.proc SETTIM
sei
sta time+0
stx time+1
sty time+2
cli
rts
.endproc
; -------------------------------------------------------------------------
; Data area - switch back to relocatable mode
.reloc
.data
spsave: .res 1
vidsave:.res 3
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