1
0
mirror of https://github.com/cc65/cc65.git synced 2024-12-23 19:29:37 +00:00
cc65/libsrc/c64/crt0.s
cuz 33c1e82bda Move zp space out of crt0.s
git-svn-id: svn://svn.cc65.org/cc65/trunk@1291 b7a2c559-68d2-44c3-8de9-860c34a00d81
2002-05-26 09:09:10 +00:00

113 lines
2.1 KiB
ArmAsm

;
; Startup code for cc65 (C64 version)
;
; This must be the *first* file on the linker command line
;
.export _exit
.import initlib, donelib
.import zerobss, push0
.import _main
.import __RAM_START__, __RAM_SIZE__ ; Linker generated
.include "zeropage.inc"
.include "c64.inc"
.include "../cbm/cbm.inc"
.code
; ------------------------------------------------------------------------
; BASIC header with a SYS call
.org $7FF
.word Head ; Load address
Head: .word @Next
.word 1000 ; Line number
.byte $9E,"2061" ; SYS 2061
.byte $00 ; End of BASIC line
@Next: .word 0 ; BASIC end marker
.reloc
; ------------------------------------------------------------------------
; Actual code
ldx #zpspace-1
L1: lda sp,x
sta zpsave,x ; Save the zero page locations we need
dex
bpl L1
; Close open files
jsr CLRCH
; Switch to second charset
lda #14
jsr BSOUT
; Clear the BSS data
jsr zerobss
; Save system stuff and setup the stack
tsx
stx spsave ; Save the system stack ptr
lda $01
sta mmusave ; Save the memory configuration
and #$F8
ora #$06 ; Enable kernal+I/O, disable basic
sta $01
lda #<(__RAM_START__ + __RAM_SIZE__)
sta sp
lda #>(__RAM_START__ + __RAM_SIZE__)
sta sp+1 ; Set argument stack ptr
; Call module constructors
jsr initlib
; Pass an empty command line
jsr push0 ; argc
jsr push0 ; argv
ldy #4 ; Argument size
jsr _main ; call the users code
; Call module destructors. This is also the _exit entry.
_exit: jsr donelib ; Run module destructors
; Restore system stuff
ldx spsave
txs ; Restore stack pointer
lda mmusave
sta $01 ; Restore memory configuration
; Copy back the zero page stuff
ldx #zpspace-1
L2: lda zpsave,x
sta sp,x
dex
bpl L2
; Reset changed vectors, back to basic
jmp RESTOR
.data
zpsave: .res zpspace
.bss
spsave: .res 1
mmusave:.res 1