;
; Startup code for cc65 (C128 version)
;
-; This must be the *first* file on the linker command line
-;
- .export _exit
- .import __hinit, initconio, doneconio, zerobss
- .import push0, doatexit, _main
+ .export _exit
+ .export __STARTUP__ : absolute = 1 ; Mark as startup
+ .import callirq, initlib, donelib
+ .import zerobss
+ .import push0, callmain
+ .import RESTOR, BSOUT, CLRCH
+ .import __INTERRUPTOR_COUNT__
+ .import __RAM_START__, __RAM_SIZE__
+
+ .include "zeropage.inc"
+ .include "c128.inc"
- .include "c128.inc"
- .include "../cbm/cbm.inc"
; ------------------------------------------------------------------------
-; Define and export the ZP variables for the C64 runtime
-
- .exportzp sp, sreg, regsave
- .exportzp ptr1, ptr2, ptr3, ptr4
- .exportzp tmp1, tmp2, tmp3, tmp4
- .exportzp regbank, zpspace
-
-sp = $02 ; stack pointer
-sreg = $04 ; secondary register/high 16 bit for longs
-regsave = $06 ; slot to save/restore (E)AX into
-ptr1 = $0A ;
-ptr2 = $0C
-ptr3 = $0E
-ptr4 = $10
-tmp1 = $12
-tmp2 = $13
-tmp3 = $14
-tmp4 = $15
-regbank = $16 ; 6 byte register bank
-zpspace = $1A ; Zero page space allocated
+; Constants
+
+IRQInd = $2FD ; JMP $0000 - used as indirect IRQ vector
; ------------------------------------------------------------------------
+; Place the startup code in a special segment to cope with the quirks of
+; c128 banking.
+
+.segment "STARTUP"
+
; BASIC header with a SYS call
.org $1BFF
.word Head ; Load address
Head: .word @Next
- .word 1000 ; Line number
+ .word .version ; Line number
.byte $9E,"7181" ; SYS 7181
.byte $00 ; End of BASIC line
@Next: .word 0 ; BASIC end marker
; ------------------------------------------------------------------------
; Actual code
- ldy #zpspace-1
-L1: lda sp,y
- sta zpsave,y ; save the zero page locations we need
- dey
- bpl L1
-
; Close open files
jsr CLRCH
-; Switch to second charset
+; Switch to the second charset
lda #14
jsr BSOUT
-; Get the current MMU setting and save it. Set new memory config.
+; Before doing anything else, we have to setup our banking configuration.
+; Otherwise just the lowest 16K are actually RAM. Writing through the ROM
+; to the underlying RAM works, but it is bad style.
lda MMU_CR ; Get current memory configuration...
pha ; ...and save it for later
- lda #$0E ; Bank0 with kernal ROM
- sta MMU_CR
+ lda #MMU_CFG_CC65 ; Bank0 with kernal ROM
+ sta MMU_CR
+
+; Save the zero page locations we need
+
+ ldx #zpspace-1
+L1: lda sp,x
+ sta zpsave,x
+ dex
+ bpl L1
; Clear the BSS data
sta mmusave
tsx
- stx spsave ; save system stk ptr
-
- lda #<$C000
- sta sp
- lda #>$C000
- sta sp+1
+ stx spsave ; Save the system stack pointer
-; Initialize the heap
+ lda #<(__RAM_START__ + __RAM_SIZE__)
+ sta sp
+ lda #>(__RAM_START__ + __RAM_SIZE__)
+ sta sp+1 ; Set argument stack ptr
- jsr __hinit
+; If we have IRQ functions, chain our stub into the IRQ vector
-; Initialize conio stuff
+ lda #<__INTERRUPTOR_COUNT__
+ beq NoIRQ1
+ lda IRQVec
+ ldx IRQVec+1
+ sta IRQInd+1
+ stx IRQInd+2
+ lda #<IRQStub
+ ldx #>IRQStub
+ sei
+ sta IRQVec
+ stx IRQVec+1
+ cli
- jsr initconio
+; Call module constructors
-; Pass an empty command line
+NoIRQ1: jsr initlib
- jsr push0 ; argc
- jsr push0 ; argv
+; Set the bank for the file name to our execution bank. We must do this,
+; *after* calling constructors, because some of them may depend on the
+; original value of this register.
- ldy #4 ; Argument size
- jsr _main ; call the users code
+ lda #0
+ sta FNAM_BANK
-; fall thru to exit...
+; Push arguments and call main()
-_exit: jsr doatexit ; call exit functions
+ jsr callmain
-; Reset the conio stuff
+; Back from main (this is also the _exit entry). Run module destructors
- jsr doneconio
+_exit: jsr donelib
-; Reset stack and the MMU
+; Reset the IRQ vector if we chained it.
- ldx spsave ; Patched at runtime
- txs
- lda mmusave ; Patched at runtime
- sta MMU_CR
+ pha ; Save the return code on stack
+ lda #<__INTERRUPTOR_COUNT__
+ beq NoIRQ2
+ lda IRQInd+1
+ ldx IRQInd+2
+ sei
+ sta IRQVec
+ stx IRQVec+1
+ cli
; Copy back the zero page stuff
- ldy #zpspace-1
-L2: lda zpsave,y
- sta sp,y
- dey
+NoIRQ2: ldx #zpspace-1
+L2: lda zpsave,x
+ sta sp,x
+ dex
bpl L2
-; Done
+; Place the program return code into ST
+
+ pla
+ sta ST
+
+; Reset the stack and the memory configuration
+
+ ldx spsave
+ txs
+ ldx mmusave
+ stx MMU_CR
+
+; Done, restore kernal vectors in an attempt to cleanup
jmp RESTOR
-.data
+; ------------------------------------------------------------------------
+; The C128 has ROM parallel to the RAM starting from $4000. The startup code
+; above will change this setting so that we have RAM from $0000-$BFFF. This
+; works quite well with the exception of interrupts: The interrupt handler
+; is in ROM, and the ROM switches back to the ROM configuration, which means
+; that parts of our program may not be accessible. To solve this, we place
+; the following code into a special segment called "LOWCODE" which will be
+; placed just above the startup code, so it goes into a RAM area that is
+; not banked.
+
+.segment "LOWCODE"
+
+IRQStub:
+ cld ; Just to be sure
+ lda MMU_CR ; Get old register value
+ pha ; And save on stack
+ lda #MMU_CFG_CC65 ; Bank 0 with kernal ROM
+ sta MMU_CR
+ jsr callirq ; Call the functions
+ pla ; Get old register value
+ sta MMU_CR
+ jmp IRQInd ; Jump to the saved IRQ vector
+
+
+; ------------------------------------------------------------------------
+; Data
+
+.segment "ZPSAVE"
+
zpsave: .res zpspace
.bss
projects / cc65 / blobdiff