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mirror of https://github.com/cc65/cc65.git synced 2024-11-12 22:07:16 +00:00
cc65/libsrc/apple2/crt0.s
cuz 3b3e1bec17 Removed the empty LOWCODE segments from the startup files. This is now
handled by the OPTIONAL segment attribute in the linker config.


git-svn-id: svn://svn.cc65.org/cc65/trunk@2164 b7a2c559-68d2-44c3-8de9-860c34a00d81
2003-05-22 22:32:04 +00:00

100 lines
1.7 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 __STARTUP_LOAD__, __BSS_LOAD__ ; Linker generated
.import callmain
.include "zeropage.inc"
.include "apple2.inc"
; ------------------------------------------------------------------------
; The executable header
.segment "EXEHDR"
.word __STARTUP_LOAD__ ; Start address
.word __BSS_LOAD__ - __STARTUP_LOAD__ ; Size
; ------------------------------------------------------------------------
; Place the startup code in a special segment.
.segment "STARTUP"
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
; Push arguments and call main()
jsr callmain
; 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
.data
zpsave: .res zpspace
.bss
spsave: .res 1