cc65/libsrc/atari/crt0.s

;
; 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, callirq
	.import		__INTERRUPTOR_COUNT__
	.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

; If we have IRQ functions, chain our stub into the IRQ vector

	lda	#<__INTERRUPTOR_COUNT__
	beq	NoIRQ1
	lda	VVBLKI
	ldx	VVBLKI+1
	sta	IRQInd+1
	stx	IRQInd+2
	lda	#6
	ldy	#<IRQStub
	ldx	#>IRQStub
	jsr	SETVBV

; Call module constructors

NoIRQ1:	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

; Reset the IRQ vector if we chained it.

	pha			; Save the return code on stack
	lda	#<__INTERRUPTOR_COUNT__
	beq	NoIRQ2
	lda	#6
	ldy	IRQInd+1
	ldx	IRQInd+2
	jsr	SETVBV

; Restore system stuff

NoIRQ2:	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

; ------------------------------------------------------------------------
; The IRQ vector jumps here, if condes routines are defined with type 2.

IRQStub:
	cld				; Just to be sure
	jsr	callirq			; Call the functions
	jmp	IRQInd			; Jump to the saved IRQ vector

; ------------------------------------------------------------------------
; Data

.data

IRQInd: jmp	$0000

; *** 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