Code & data for "system check" load chunk in the atarixl target.

libsrc/atari/system_check.s

@@ -0,0 +1,159 @@
+;
+; Atari XL startup system check
+;
+; This routine gets loaded prior to the main part of the executable
+; and checks if the system is compatible to run the program.
+; It checks whether the system is an XL type one and that enough
+; memory is installed (which isn't the case for a 600XL).
+; If the system doesn't qualify, the loading of the main program
+; is aborted by jumping to DOSVEC.
+;
+; Christian Groessler, chris@groessler.org, 2013
+;
+
+.if .defined(__ATARIXL__)
+
+	.export		syschk
+        .import         __SYSCHK_LOAD__
+        .import         __SAVEAREA_LOAD__
+
+        .include        "zeropage.inc"
+        .include        "atari.inc"
+
+
+.macro print_string text
+	.local	start, cont
+	jmp	cont
+start:	.byte	text, ATEOL
+cont:	ldx	#0		; channel 0
+	lda	#<start
+	sta	ICBAL,x		; address
+	lda	#>start
+	sta	ICBAH,x
+	lda	#<(cont - start)
+	sta	ICBLL,x		; length
+	lda	#>(cont - start)
+	sta	ICBLH,x
+	lda	#PUTCHR
+	sta	ICCOM,x
+	jsr	CIOV
+.endmacro
+.macro print_string2 addr, len
+
+	ldx	#0		; channel 0
+	lda	#<addr
+	sta	ICBAL,x		; address
+	lda	#>addr
+	sta	ICBAH,x
+	lda	#<len
+	sta	ICBLL,x		; length
+	lda	#>len
+	sta	ICBLH,x
+	lda	#PUTCHR
+	sta	ICCOM,x
+	jsr	CIOV
+
+.endmacro
+
+
+; ------------------------------------------------------------------------
+; Chunk header
+
+.segment        "SYSCHKHDR"
+
+        .word   __SYSCHK_LOAD__
+        .word   trailer - 1
+
+; ------------------------------------------------------------------------
+; Actual code
+
+.segment        "SYSCHK"
+
+syschk:
+	lda     $fcd8		; from ostype.s
+        cmp     #$a2
+        bne     is_xl
+
+; no XL machine
+	print_string "This program needs an XL machine."
+	jmp	fail
+
+; we have an XL machine, now check memory
+is_xl:	lda	RAMSIZ
+	cmp	#$80
+	bcs	sys_ok
+
+; not enough memory
+	print_string "Not enough memory."
+fail:	jsr	delay
+	jmp	(DOSVEC)
+
+lowadr:	.res	2		; lowest address we need in order to move screen memory down, depending on start address of program
+
+
+; system is basically supported, check if there is enough space btw. MEMLO and our start address
+; to move screen memory there
+
+CMPVAL = 64+255+992		; you may ask, why these values...   @@@ document
+
+sys_ok:	lda	#<__SAVEAREA_LOAD__
+	sec
+	sbc	#<CMPVAL
+	sta	lowadr
+	lda	#>__SAVEAREA_LOAD__
+	sbc	#>CMPVAL
+	sta	lowadr+1
+
+	sec
+	lda	MEMLO
+	sbc	lowadr
+	lda	MEMLO+1
+	sbc	lowadr+1
+	bcc	memlo_ok
+
+; load address was too low
+	print_string2 lmemerr_txt, lmemerr_txt_len
+	jsr	delay		; long text takes longer to read, give user additional time
+	jmp	fail
+
+; all is well(tm), launch the application
+memlo_ok:
+	rts
+
+
+lmemerr_txt:
+	.byte	"Not enough memory to move screen", ATEOL
+	.byte	"memory to low memory. Consider using", ATEOL
+	.byte	"a higher load address.", ATEOL
+lmemerr_txt_len	= * - lmemerr_txt
+
+
+; short delay
+.proc	delay
+
+	lda	#10
+l:	jsr	delay1
+	clc
+	sbc	#0
+	bne	l
+	rts
+
+delay1:	ldx	#0
+	ldy	#0
+loop:	dey
+	bne	loop
+	dex
+	bne	loop
+	rts
+
+.endproc
+
+; ------------------------------------------------------------------------
+; Chunk "trailer" - sets INITAD
+
+trailer:
+        .word   INITAD
+        .word   INITAD+1
+        .word   __SYSCHK_LOAD__
+
+.endif	; .if .defined(__ATARIXL__)