text: move: sorta working

textmode/textscroll/comet.s

@@ -0,0 +1,164 @@
+
+CH	= $24
+CV	= $25
+BASL	= $28
+BASH	= $29
+SEEDL	= $4E
+FACL	= $9D
+FACH	= $9E
+
+DRAW_PAGE	= $FF
+
+PAGE0		= $C054
+GETCHAR		= $D72C
+HGR		= $F3E2
+SETTXT		= $FB39
+TABV		= $FB5B		; store A in CV and call MON_VTAB
+STORADV		= $FBF0		; store A at (BASL),CH, advancing CH, trash Y
+MON_VTAB	= $FC22		; VTAB to CV
+VTABZ		= $FC24		; VTAB to value in A
+HOME		= $FC58
+WAIT    = $FCA8                 ;; delay 1/2(26+27A+5A^2) us
+
+COUT	= $FDED
+COUT1	= $FDF0
+COUTZ	= $FDF6		; cout but ignore inverse flag
+
+ypos	= $2000
+xpos	= $2100
+textl	= $2200
+texth	= $2300
+
+move:
+	jsr	HGR
+
+	sta	DRAW_PAGE
+
+	jsr	SETTXT
+
+
+next_frame:
+	ldx	#0
+next_text:
+	lda	xpos,X
+	bne	not_new
+
+new_text:
+	jsr	random8
+	and	#$1f
+	adc	#$4
+	sta	xpos,X
+
+	jsr	random8
+	and	#$f
+	sta	ypos,X
+
+	lda	#<text
+	sta	textl,X
+	lda	#>text
+	sta	texth,X
+
+not_new:
+	lda	xpos,X
+	sta	CH
+	lda	ypos,X
+	sta	CV
+
+	jsr	MON_VTAB
+
+	lda	BASH
+	clc
+	adc	DRAW_PAGE
+	sta	BASH
+
+
+	ldy	#0
+	lda	textl,X
+	sta	FACL
+	lda	texth,X
+	sta	FACH
+
+	txa
+	pha
+
+print_loop:
+	jsr	GETCHAR
+
+	php
+
+	ora	#$80
+	jsr	STORADV
+
+	plp
+
+	bpl	print_loop
+
+big_done:
+
+	pla
+	tax
+
+	dec	xpos,X
+
+	inx
+	cpx	#20
+	bne	next_text
+
+flip_pages:
+	ldx	#0
+
+	lda     DRAW_PAGE
+	beq	done_page
+	inx
+done_page:
+	ldy	PAGE0,X         ; set display page to PAGE1 or PAGE2
+
+	eor	#$4             ; flip draw page between $400/$800
+        sta	DRAW_PAGE
+
+	clc
+	adc	#$4
+	sta	BASH
+	lda	#$0
+	sta	BASL
+
+clear_screen_outer:
+	ldy	#$f8
+clear_screen_inner:
+	lda	#$A0		; space char
+	sta	(BASL),Y	; 100 101 110 111
+	dey
+	cpy	#$FF
+	bne	clear_screen_inner
+	inc	BASH
+	lda	BASH
+	and	#$3
+	bne	clear_screen_outer
+
+	lda	#$50
+	jsr	WAIT
+
+	jmp	next_frame
+
+
+	;=============================
+        ; random8
+        ;=============================
+        ; 8-bit 6502 Random Number Generator
+        ; Linear feedback shift register PRNG by White Flame
+        ; http://codebase64.org/doku.php?id=base:small_fast_8-bit_prng
+
+random8:
+        lda     SEEDL                                                   ; 2
+        beq     doEor                                                   ; 2
+        asl                                                             ; 1
+        beq     noEor   ; if the input was $80, skip the EOR            ; 2
+        bcc     noEor                                                   ; 2
+doEor:  eor     #$1d                                                    ; 2
+noEor:  sta     SEEDL                                                   ; 2
+	rts
+
+
+text:
+	.byte "HELL",'O'|$80
+

textmode/textscroll/move.s

@@ -4,11 +4,14 @@ CV	= $25
 BASL	= $28
 BASH	= $29
 SEEDL	= $4E
+FACL	= $9D
+FACH	= $9E
 
+COUNT		= $FE
 DRAW_PAGE	= $FF
 
 PAGE0		= $C054
-
+GETCHAR		= $D72C		; loads (FAC),Y and increments FAC
 HGR		= $F3E2
 SETTXT		= $FB39
 TABV		= $FB5B		; store A in CV and call MON_VTAB
@@ -24,6 +27,8 @@ COUTZ	= $FDF6		; cout but ignore inverse flag
 
 ypos	= $2000
 xpos	= $2100
+textl	= $2200
+texth	= $2300
 
 move:
 	jsr	HGR
@@ -49,6 +54,33 @@ new_text:
 	and	#$f
 	sta	ypos,X
 
+	jsr	random8
+	and	#$7f
+	sta	COUNT
+
+	lda	#$d0		; token table at $D0D0
+	sta	FACL
+	sta	FACH
+
+	ldy	#0
+find_token_loop:
+	dec	COUNT
+	bmi	found_token
+find_token_inner:
+	inc	FACL
+	bne	blargh
+	inc	FACH
+blargh:
+	lda	(FACL),Y
+	bpl	find_token_inner
+	bmi	find_token_loop
+
+found_token:
+	inc	FACL
+	lda	FACL
+	sta	textl,X
+	lda	FACH
+	sta	texth,X
 
 not_new:
 	lda	xpos,X
@@ -63,17 +95,25 @@ not_new:
 	adc	DRAW_PAGE
 	sta	BASH
 
+	lda	textl,X
+	sta	text_smc+1
+	lda	texth,X
+	sta	text_smc+2
+
 	txa
 	pha
 
 	ldx	#0
 print_loop:
-	lda	text,X
+
+text_smc:
+	lda	$dddd,X
 
 	php
 
 	ora	#$80
-	jsr	STORADV
+	jsr	STORADV		; trashes Y :(
+
 	inx
 
 	plp
@@ -88,7 +128,7 @@ big_done:
 	dec	xpos,X
 
 	inx
-	cpx	#20
+	cpx	#32
 	bne	next_text
 
 flip_pages:
@@ -122,7 +162,7 @@ clear_screen_inner:
 	and	#$3
 	bne	clear_screen_outer
 
-	lda	#$50
+	lda	#200
 	jsr	WAIT
 
 	jmp	next_frame
@@ -146,6 +186,5 @@ noEor:  sta     SEEDL                                                   ; 2
 	rts
 
 
-text:
+
-	.byte "HELL",'O'|$80