;
; Startup code for cc65 (CBM 500 version)
-;
-; This must be the *first* file on the linker command line
;
.export _exit
- .import initlib, donelib
- .import push0, _main
- .import __BSS_RUN__, __BSS_SIZE__
- .import irq, nmi
- .import k_irq, k_nmi, k_plot, k_udtim, k_scnkey
+ .export __STARTUP__ : absolute = 1 ; Mark as startup
- .include "zeropage.inc"
- .include "io.inc"
+ .import _clrscr, initlib, donelib, callirq_y
+ .import push0, callmain
+ .import __CHARRAM_START__, __CHARRAM_SIZE__, __VIDRAM_START__
+ .import __BSS_RUN__, __BSS_SIZE__, __EXTZP_RUN__
+ .import __INTERRUPTOR_COUNT__
+ .import scnkey, UDTIM
+ .include "zeropage.inc"
+ .include "extzp.inc"
+ .include "cbm510.inc"
-; ------------------------------------------------------------------------
-; Define and export the ZP variables for the CBM510 runtime
-
- .exportzp sp, sreg, regsave
- .exportzp ptr1, ptr2, ptr3, ptr4
- .exportzp tmp1, tmp2, tmp3, tmp4
- .exportzp regbank, zpspace
- .exportzp vic, sid, IPCcia, cia, acia, tpi1, tpi2
- .exportzp ktab1, ktab2, ktab3, ktab4, time, RecvBuf, SendBuf
-
-.zeropage
-
-zpstart = *
-sp: .res 2 ; Stack pointer
-sreg: .res 2 ; Secondary register/high 16 bit for longs
-regsave: .res 2 ; slot to save/restore (E)AX into
-ptr1: .res 2
-ptr2: .res 2
-ptr3: .res 2
-ptr4: .res 2
-tmp1: .res 1
-tmp2: .res 1
-tmp3: .res 1
-tmp4: .res 1
-regbank: .res 6 ; 6 byte register bank
-
-zpspace = * - zpstart ; Zero page space allocated
-
-.code
; ------------------------------------------------------------------------
; BASIC header and a small BASIC program. Since it is not possible to start
; that is overwritten later.
;
-; To make things more simple, make the code of this module absolute.
+.segment "BASICHDR"
- .org $0001
-Head: .byte $03,$00,$11,$00,$0a,$00,$81,$20,$49,$b2,$30,$20,$a4,$20,$34,$00
+ .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
-; Since we need some vectors to access stuff in the system bank for our own,
-; we will include them here, starting from $60:
+;------------------------------------------------------------------------------
+; A table that contains values that must be transfered from the system zero
+; page into out zero page. Contains pairs of bytes, first one is the address
+; in the system ZP, second one is our ZP address. The table goes into page 2,
+; but is declared here, because it is needed earlier.
+
+.SEGMENT "PAGE2"
+
+.proc transfer_table
+
+ .byte $CA, CURS_Y
+ .byte $CB, CURS_X
+ .byte $EC, CHARCOLOR
+
+.endproc
+
+
+;------------------------------------------------------------------------------
+; Page 3 data. This page contains the break vector and the bankswitch
+; subroutine that is copied into high memory on startup. The space occupied by
+; this routine will later be used for a copy of the bank 15 stack. It must be
+; saved, since we're going to destroy it when calling bank 15.
+
+.segment "PAGE3"
+
+BRKVec: .addr _exit ; BRK indirect vector
+
+.proc callbank15
+
+ excrts = $FEFE
+
+.org $FEC3
+
+entry: php
+ pha
+ lda #$0F ; Bank 15
+ sta IndReg
+ txa
+ pha
+ tya
+ pha
+ sei
+ ldy #$FF
+ lda (sysp1),y
+ tay
+ lda ExecReg
+ sta (sysp1),y
+ dey
+
+ lda #.hibyte(excrts-1)
+ sta (sysp1),y
+ dey
+ lda #.lobyte(excrts-1)
+ sta (sysp1),y
+
+ tya
+ sec
+ sbc #7
+ sta $1FF ; Save new sp
+ tay
+
+ tsx
+
+ pla
+ iny
+ sta (sysp1),y
+ pla
+ iny
+ sta (sysp1),y
+ pla
+ iny
+ sta (sysp1),y
+ pla
+ iny
+ sta (sysp1),y
+
+ lda $105,x
+ sec
+ sbc #3
+ iny
+ sta (sysp1),y
+ lda $106,x
+ sbc #0
+ iny
+ sta (sysp1),y
+
+ ldy $1FF ; Restore sp in bank 15
+
+ lda #.hibyte(expull-1)
+ sta (sysp1),y
+ dey
+ lda #.lobyte(expull-1)
+ sta (sysp1),y
+ dey
+ pla
+ pla
+ tsx
+ stx $1FF
+ tya
+ tax
+ txs
+ lda IndReg
+ jmp $FFF6
+
+expull: pla
+ tay
+ pla
+ tax
+ pla
+ plp
+ rts
- .res $60-*
+.if (expull <> $FF26)
+.error "Symbol expull must be aligned with kernal in bank 15"
+.endif
-vic: .word $d800
-sid: .word $da00
-IPCcia: .word $db00
-cia: .word $dc00
-acia: .word $dd00
-tpi1: .word $de00
-tpi2: .word $df00
-ktab1: .word $eab1
-ktab2: .word $eb11
-ktab3: .word $eb71
-ktab4: .word $ebd1
-time: .dword $0000
-RecvBuf: .word $0100 ; RS232 received buffer
-SendBuf: .word $0200 ; RS232 send buffer
+.reloc
+.endproc
+;------------------------------------------------------------------------------
; 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
+.segment "STARTUP"
+
+Back: 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:
+; We are at $100 now. The following snippet 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 #$01
+ lda #$00
sta ExecReg
; This is the actual starting point of our code after switching banks for
; startup. Beware: The following code will get overwritten as soon as we
-; use the stack (since it's in page 1)!
+; use the stack (since it's in page 1)! We jump to another location, since
+; we need some space for subroutines that aren't used later.
- tsx
- stx spsave ; Save the system stackpointer
- ldx #$FF
- txs ; Set up our own stack
+ jmp Origin
-; Set the interrupt, NMI and other vectors
+; Hardware vectors, copied to $FFFA
- ldy #vectable_size
-L0: lda vectable-1,y
- sta $FF80,y
- dey
- bne L0
+.proc vectors
+ sta ExecReg
+ rts
+ nop
+ .word nmi ; NMI vector
+ .word 0 ; Reset - not used
+ .word irq ; IRQ vector
+.endproc
+
+; Initializers for the extended zeropage. See extzp.s
+
+.proc extzp
+ .word $0100 ; sysp1
+ .word $0300 ; sysp3
+ .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
+.endproc
; Switch the indirect segment to the system bank
- lda #$0F
+Origin: lda #$0F
sta IndReg
-; Copy the kernal zero page ($90-$F2) from the system bank
+; Initialize the extended zeropage
+
+ ldx #.sizeof(extzp)-1
+L1: lda extzp,x
+ sta <__EXTZP_RUN__,x
+ dex
+ bpl L1
+
+; Save the old stack pointer from the system bank and setup our hw sp
+
+ tsx
+ txa
+ ldy #$FF
+ sta (sysp1),y ; Save system stack point into $F:$1FF
+ ldx #$FE ; Leave $1FF untouched for cross bank calls
+ txs ; Set up our own stack
+
+; Copy stuff from the system zeropage to ours
+
+ lda #.sizeof(transfer_table)
+ sta ktmp
+L2: ldx ktmp
+ ldy transfer_table-2,x
+ lda transfer_table-1,x
+ tax
+ lda (sysp0),y
+ sta $00,x
+ dec ktmp
+ dec ktmp
+ bne L2
- lda #$90
- sta ptr1
- lda #$00
- sta ptr1+1
- ldy #$62-1
-L1: lda (ptr1),y
- sta $90,y
- dey
- bpl L1
+; Set the interrupt, NMI and other vectors
-; Copy the page 3 vectors in place
+ ldx #.sizeof(vectors)-1
+L3: lda vectors,x
+ sta $10000 - .sizeof(vectors),x
+ dex
+ bpl L3
- ldy #$00
-L2: lda p3vectable,y
- sta $300,y
- iny
- cpy #p3vectable_size
- bne L2
+; Setup the C stack
-; Copy the rest of page 3 from the system bank
+ lda #.lobyte(callbank15::entry)
+ sta sp
+ lda #.hibyte(callbank15::entry)
+ sta sp+1
- lda #$00
- sta ptr1
- lda #$03
- sta ptr1+1
-L3: lda (ptr1),y
- sta $300,y
- iny
- bne L3
+; Setup the subroutine and jump vector table that redirects kernal calls to
+; the system bank.
+
+ ldy #.sizeof(callbank15)
+@L1: lda callbank15-1,y
+ sta callbank15::entry-1,y
+ dey
+ bne @L1
+
+; Setup the jump vector table. Y is zero on entry.
+
+ ldx #45-1 ; Number of vectors
+@L2: lda #$20 ; JSR opcode
+ sta $FF6F,y
+ iny
+ lda #.lobyte(callbank15::entry)
+ sta $FF6F,y
+ iny
+ lda #.hibyte(callbank15::entry)
+ sta $FF6F,y
+ iny
+ dex
+ bpl @L2
; Set the indirect segment to bank we're executing in
- lda ExecReg
- sta IndReg
+ 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,
iny
bne Z1
inc ptr1+1 ; Next page
- dex
+ dex
bne Z1
; Clear the remaining page
iny
dex
bne Z3
-Z4:
+Z4: jmp Init
-; Setup the C stack
+; ------------------------------------------------------------------------
+; We are at $200 now. We may now start calling subroutines safely, since
+; the code we execute is no longer in the stack page.
- lda #<$FF81
- sta sp
- lda #>$FF81
- sta sp+1
+.segment "PAGE2"
-; We expect to be in page 2 now
+; Copy the character rom from the system bank into the execution bank
-.if (* < $1FD)
- jmp $200
- .res $200-*
-.endif
-.if (* < $200)
- .res $200-*,$EA
-.endif
-.if (* >= $2F0)
-.error "Code range invalid"
-.endif
+Init: lda #<$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 #TPI::CR
+ 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 #TPI::PRC
+ 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
+
+; Activate chained interrupt handlers, then enable interrupts.
+
+ lda #.lobyte(__INTERRUPTOR_COUNT__*2)
+ sta irqcount
+ cli
-; 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.
-; Call module constructors
+; Call module constructors.
- jsr initlib
+ jsr initlib
-; Create the (empty) command line for the program
+; Push arguments and call main()
- jsr push0 ; argc
- jsr push0 ; argv
+ jsr callmain
-; Execute the program code
+; Call module destructors. This is also the _exit entry and the default entry
+; point for the break vector.
- jmp Start
+_exit: pha ; Save the return code on stack
+ jsr donelib ; Run module destructors
+ lda #$00
+ sta irqcount ; Disable custom irq handlers
-; ------------------------------------------------------------------------
-; Additional data that we need for initialization and that's overwritten
-; later
-
-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 k_scnkey ; 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 k_setlfs ; SETLFS
- jmp k_setnam ; 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 k_settim ; SETTIM
- jmp k_rdtim ; RDTIM
- jmp $0000 ; STOP
- jmp $0000 ; GETIN
- jmp $0000 ; CLALL
- jmp k_udtim ; UDTIM
- jmp k_screen ; SCREEN
- jmp k_plot ; PLOT
- jmp k_iobase ; IOBASE
- sta ExecReg
- rts
- .byte $01 ; Filler
- .word nmi
- .word 0 ; Reset - not used
- .word irq
-vectable_size = * - vectable
+; Address the system bank
-p3vectable:
- .word k_irq ; IRQ user vector
- .word k_brk ; BRK user vector
- .word k_nmi ; NMI user vector
-p3vectable_size = * - p3vectable
+ lda #$0F
+ sta IndReg
+; Switch back the video to the system bank
-; ------------------------------------------------------------------------
-; This is the program code after setup. It starts at $400
-
- .res $400-*
+ ldy #TPI::CR
+ lda vidsave+0
+ sta (tpi1),y
-Start:
+ ldy #TPI::PRC
+ lda vidsave+1
+ sta (tpi2),y
-; Enable interrupts
+ ldy #VIC_VIDEO_ADR
+ lda vidsave+2
+ sta (vic),y
- cli
+; Copy stuff back from our zeropage to the systems
-; Call the user code
+.if 0
+ lda #.sizeof(transfer_table)
+ sta ktmp
+@L0: ldx ktmp
+ ldy transfer_table-2,x
+ lda transfer_table-1,x
+ tax
+ lda $00,x
+ sta (sysp0),y
+ dec ktmp
+ dec ktmp
+ bne @L0
+.endif
- ldy #4 ; Argument size
- jsr _main ; call the users code
+; Place the program return code into ST
-; Call module destructors. This is also the _exit entry.
+ pla
+ ldy #$9C ; ST
+ sta (sysp0),y
-_exit: jsr donelib ; Run module destructors
+; Setup the welcome code at the stack bottom in the system bank.
-; Clear the start of the zero page, since it will be interpreted as a
-; (garbage) BASIC program otherwise. This is also the default entry for
-; the break vector.
+ ldy #$FF
+ lda (sysp1),y ; Load system bank sp
+ tax
+ iny ; Y = 0
+ lda #$58 ; CLI opcode
+ sta (sysp1),y
+ iny
+ lda #$60 ; RTS opcode
+ sta (sysp1),y
+ lda IndReg
+ sei
+ txs
+ jmp Back
-k_brk: sei
- lda #$00
- ldx #$3E
-Clear: sta $02,x
- dex
- bne Clear
+; -------------------------------------------------------------------------
+; The IRQ handler goes into PAGE2. For performance reasons, and to allow
+; easier chaining, we do handle the IRQs in the execution bank (instead of
+; passing them to the system bank).
-; Setup the welcome code at the stack bottom in the system bank. Use
-; the F4/F5 vector to access the system bank
+; This is the mapping of the active irq register of the 6525 (tpi1):
+;
+; Bit 7 6 5 4 3 2 1 0
+; | | | | ^ 50 Hz
+; | | | ^ SRQ IEEE 488
+; | | ^ cia
+; | ^ IRQB ext. Port
+; ^ acia
+
+irq: pha
+ txa
+ pha
+ tya
+ pha
+ lda IndReg
+ pha
+ lda ExecReg
+ sta IndReg ; Be sure to address our segment
+ tsx
+ lda $105,x ; Get the flags from the stack
+ and #$10 ; Test break flag
+ bne dobrk
+
+; It's an IRQ
+
+ cld
+
+; Call chained IRQ handlers
+
+ ldy irqcount
+ beq irqskip
+ jsr callirq_y ; Call the functions
+
+; Done with chained IRQ handlers, check the TPI for IRQs and handle them
+
+irqskip:lda #$0F
+ sta IndReg
+ ldy #TPI::AIR
+ lda (tpi1),y ; Interrupt Register 6525
+ beq noirq
- lda #$0F
- sta IndReg
- ldy #$00
- sty $F4
- iny
- sty $F5
- ldy #reset_size-1
-@L1: lda reset,y
- sta ($F4),y
- dey
- bne @L1
- jmp Back
+; 50/60Hz interrupt
-; ------------------------------------------------------------------------
-; Code that is copied into the system bank at $100 when switching back
+ cmp #%00000001 ; ticker irq?
+ bne irqend
+ jsr scnkey ; Poll the keyboard
+ jsr UDTIM ; Bump the time
-reset: cli
- jmp $8000 ; BASIC cold start
-reset_size = * - reset
+; Done
-; ------------------------------------------------------------------------
-; Code for a few simpler kernal calls goes here
-
-k_iobase:
- ldx cia
- ldy cia+1
- rts
-
-k_screen:
- ldx #40 ; Columns
- ldy #25 ; Lines
- rts
-
-k_setlfs:
- sta LogicalAdr
- stx FirstAdr
- sty SecondAdr
- rts
+irqend: ldy #TPI::AIR
+ sta (tpi1),y ; Clear interrupt
-k_setnam:
- sta FileNameLen
- lda $00,x
- sta FileNameAdrLo
- lda $01,x
- sta FileNameAdrHi
- lda $02,x
- sta FileNameAdrSeg
- rts
+noirq: pla
+ sta IndReg
+ pla
+ tay
+ pla
+ tax
+ pla
+nmi: rti
-k_rdtim:
- sei
- lda time+0
- ldx time+1
- ldy time+2
- cli
- rts
-
-k_settim:
- sei
- sta time+0
- stx time+1
- sty time+2
- cli
- rts
+dobrk: jmp (BRKVec)
; -------------------------------------------------------------------------
-; Data area - switch back to relocatable mode
-
- .reloc
+; Data area
.data
-spsave: .res 1
+vidsave:.res 3
+.bss
+irqcount: .byte 0
projects / cc65 / blobdiff