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cc65/libsrc/atari/crt0.s

167 lines
3.4 KiB
ArmAsm

;
; Startup code for cc65 (ATARI version)
;
; Contributing authors:
; Mark Keates
; Freddy Offenga
; Christian Groessler
; Stefan Haubenthal
;
.export _exit
.export __STARTUP__ : absolute = 1 ; Mark as startup
.import initlib, donelib
.import callmain, zerobss
.import __STARTUP_LOAD__, __ZPSAVE_LOAD__
.import __RESERVED_MEMORY__
.include "zeropage.inc"
.include "atari.inc"
; ------------------------------------------------------------------------
; EXE header
.segment "EXEHDR"
.word $FFFF
.word __STARTUP_LOAD__
.word __ZPSAVE_LOAD__ - 1
; ------------------------------------------------------------------------
; Actual code
.segment "STARTUP"
rts ; fix for SpartaDOS / OS/A+
; they first call the entry point from AUTOSTRT and
; then the load addess (this rts here).
; We point AUTOSTRT directly after the rts.
; Real entry point:
; Save the zero page locations we need
ldx #zpspace-1
L1: lda sp,x
sta zpsave,x
dex
bpl L1
; Clear the BSS data
jsr zerobss
; Setup the stack
tsx
stx spsave
; Report memory usage
lda APPMHI
sta appmsav ; remember old APPMHI value
lda APPMHI+1
sta appmsav+1
sec
lda MEMTOP
sbc #<__RESERVED_MEMORY__
sta APPMHI ; initialize our APPMHI value
sta sp ; setup runtime stack part 1
lda MEMTOP+1
sbc #>__RESERVED_MEMORY__
sta APPMHI+1
sta sp+1 ; setup runtime stack part 2
; Call module constructors
jsr initlib
; Set left margin to 0
lda LMARGN
sta old_lmargin
ldy #0
sty LMARGN
; Set keyb to upper/lowercase mode
ldx SHFLOK
stx old_shflok
sty SHFLOK
; Initialize conio stuff
dey ; Set X to $FF
sty CH
; Push arguments and call main
jsr callmain
; Call module destructors. This is also the _exit entry.
_exit: jsr donelib ; Run module destructors
; Restore system stuff
ldx spsave
txs ; Restore stack pointer
; Restore left margin
lda old_lmargin
sta LMARGN
; Restore kb mode
lda old_shflok
sta SHFLOK
; Restore APPMHI
lda appmsav
sta APPMHI
lda appmsav+1
sta APPMHI+1
; Copy back the zero page stuff
ldx #zpspace-1
L2: lda zpsave,x
sta sp,x
dex
bpl L2
; Turn on cursor
inx
stx CRSINH
; Back to DOS
rts
; *** end of main startup code
; ------------------------------------------------------------------------
.segment "ZPSAVE"
zpsave: .res zpspace
; ------------------------------------------------------------------------
.bss
spsave: .res 1
appmsav: .res 1
old_shflok: .res 1
old_lmargin: .res 1
.segment "AUTOSTRT"
.word RUNAD ; defined in atari.h
.word RUNAD+1
.word __STARTUP_LOAD__ + 1