****************************************
* SHR1                                 *
*                                      *
*  Dagen Brock <dagenbrock@gmail.com>  *
*  2013-07-17                          *
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	rel	; Compile 
	dsk SHR1.l	; Save Name
	mx %00	; Program starts in 16-bit mode

	phk	; Set Data Bank to Program Bank
	plb	; Always do this first!

GraphicsOn	sep #$30	; 8-bit mode
	lda #$81
	stal $00C029	; Turn on SHR mode
	rep #$30	; back to 16-bit mode

	jsr WaitKey	; pause



ClearNaive	ldx #$0000	; Start at first pixel
	lda #$0000	; store zeros
:clearloop	stal $E12000,x  ; screen location
	inx
	inx
	cpx #$8000	; see if we've filled entire frame/colors/scbs
	bne :clearloop	; pause


	jsr WaitKey



ClearFaster	ldx #$7FFE	; start at top this time
	lda #$0000	; store zeros
:clearloop	stal $E12000,x	; screen location
	dex
	dex
		; avoid 16K "compare X's" for  80K cycle savings
	bne :clearloop	; loop until we've worked our way down to 0
	jsr WaitKey


	jsl $E100A8	; Prodos 16 entry point
	da $29	; Quit code
	adrl QuitParm	; address of parameter table
	bcs Error	; never taken

Error	brk	; should never get here

QuitParm	adrl $0000	; pointer to pathname (not used here)
	da $00	; quit type (absolute quite)

WaitKey	sep #$30	; good old apple ii key wait routine
:wait	ldal $00C000	;  but called using long addressing modes
	bpl :wait	;  in 8-bit mode
	stal $00C010
	rep #$30
	rts