Code & data for "shadow RAM preparation" load chunk in the atarixl target.

Intermediate check-in, unfinished...

libsrc/atari/shadow_ram_prepare.s

@@ -0,0 +1,185 @@
+;
+; Atari XL shadow RAM preparation routines
+;
+; Tasks:
+; - move screen memory below load address
+; - copy shadow RAM contents to their destination
+;
+; Christian Groessler, chris@groessler.org, 2013
+;
+
+.if .defined(__ATARIXL__)
+
+	.export		sramprep
+        .import         __SRPREP_LOAD__, __SRPREP_SIZE__
+	.import		__SHADOW_RAM_LOAD__, __SHADOW_RAM_SIZE__
+	.import		__CHARGEN_LOAD__, __CHARGEN_SIZE__
+	.import		__SAVEAREA_LOAD__
+
+        .include        "zeropage.inc"
+        .include        "atari.inc"
+	.include	"save_area.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
+
+; ------------------------------------------------------------------------
+; Chunk header
+
+.segment        "SRPREPHDR"
+
+        .word   __SRPREP_LOAD__
+        .word   __SRPREP_LOAD__ + __SRPREP_SIZE__ - 1
+
+; ------------------------------------------------------------------------
+; Actual code
+
+.segment        "SRPREP"
+
+sramprep:
+	print_string "in sramprep"
+
+; save values of modified system variables and ports
+	lda	RAMTOP
+	sta	RAMTOP_save
+	lda	MEMTOP
+	sta	MEMTOP_save
+	lda	MEMTOP+1
+	sta	MEMTOP_save+1
+	lda	APPMHI
+	sta	APPMHI_save
+	lda	APPMHI+1
+	sta	APPMHI_save+1
+	lda	PORTB
+	sta	PORTB_save
+
+; disable BASIC
+
+	lda	PORTB
+	ora	#2
+	sta	PORTB
+
+
+; ... change memory bla
+
+CMPVAL = 64+255+992		; you may ask, why these values...   @@@ document
+
+sys_ok:	lda	#<__SAVEAREA_LOAD__
+	sec
+	sbc	#<CMPVAL
+	sta	MEMTOP
+	sta	APPMHI
+	lda	#>__SAVEAREA_LOAD__
+	sbc	#>CMPVAL
+	sta	MEMTOP+1
+	sta	APPMHI+1
+
+	lda	#>__SAVEAREA_LOAD__ - 1
+	sta	RAMTOP
+	
+	
+
+; ... issue ar GRAPHICS 0 call (copied'n'pasted from TGI drivers)
+
+
+	ldx	#$50		; take any IOCB, hopefully free (@@@ fixme)
+
+        ; Reopen it in Graphics 0
+        lda     #OPEN
+        sta     ICCOM,x
+        lda     #OPNIN | OPNOT
+        sta     ICAX1,x
+        lda     #0
+        sta     ICAX2,x
+        lda     #<screen_device
+        sta     ICBAL,x
+        lda     #>screen_device
+        sta     ICBAH,x
+        lda     #<screen_device_length
+        sta     ICBLL,x
+        lda     #>screen_device_length
+        sta     ICBLH,x
+        jsr     CIOV
+	bpl	okoko
+
+	print_string "GR 0 FAILED"
+	jsr	delay
+	jsr	delay
+	jsr	delay
+
+	jmp xxx
+
+okoko:
+
+
+        ; Now close it again; we don't need it anymore :)
+        lda     #CLOSE
+        sta     ICCOM,x
+        jsr     CIOV
+
+	print_string "GR 0 OKOKO"
+	jsr	delay
+
+
+
+
+
+
+xxx:
+
+
+
+
+
+        rts
+
+; 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
+
+screen_device:	.byte "S:",0
+screen_device_length = * - screen_device
+
+	.byte	" ** srprep ** end-->"
+
+; ------------------------------------------------------------------------
+; Chunk "trailer" - sets INITAD
+
+.segment        "SRPREPTRL"
+
+        .word   INITAD
+        .word   INITAD+1
+        .word   __SRPREP_LOAD__
+
+.endif	; .if .defined(__ATARIXL__)