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mirror of https://github.com/cc65/cc65.git synced 2024-12-23 04:30:10 +00:00
cc65/libsrc/apple2/crt0.s
cuz 55dfc0f312 Use MEMSIZE instead of using a fixed high mem location
git-svn-id: svn://svn.cc65.org/cc65/trunk@1354 b7a2c559-68d2-44c3-8de9-860c34a00d81
2002-07-15 20:03:37 +00:00

102 lines
1.6 KiB
ArmAsm

;
; Startup code for cc65 (Apple2 version)
;
; This must be the *first* file on the linker command line
;
.export _exit
.import initlib, donelib
.import zerobss, push0
.import __CODE_LOAD__, __BSS_LOAD__ ; Linker generated
.import _main
.include "zeropage.inc"
.include "apple2.inc"
; ------------------------------------------------------------------------
; The executable header
.segment "EXEHDR"
.word __CODE_LOAD__ ; Start address
.word __BSS_LOAD__ - __CODE_LOAD__ ; Size
; ------------------------------------------------------------------------
; Actual code
.code
ldx #zpspace-1
L1: lda sp,x
sta zpsave,x ; Save the zero page locations we need
dex
bpl L1
; Clear the BSS data
jsr zerobss
; Save system stuff and setup the stack
tsx
stx spsave ; Save the system stack ptr
lda MEMSIZE
sta sp
lda MEMSIZE+1
sta sp+1 ; Set argument stack ptr
; Call module constructors
jsr initlib
; Initialize conio stuff
lda #$ff
sta TEXTTYP
; Set up to use Apple ROM $C000-$CFFF
;; sta USEROM
; 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
; Restore system stuff
lda #$ff ; Reset text mode
sta TEXTTYP
ldx spsave
txs ; Restore stack pointer
; 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