; My VIS 40 Project: 1-pixel video.
; Spencer Wohlers
; May 9, 2008

.nolist
#include "ti83plus.inc"
#define    ProgStart    $9D95
.list
.org    ProgStart - 2
.db     t2ByteTok, tAsmCmp
; Title screen goes here.
	b_call(_ClrLCDFull)		; clear LCD
	b_call(_HomeUp)			; resets to (0,0)
	ld	hl, introtext1		; load address
	b_call(_PutS)			; prints string of text
	b_call(_NewLine)		; spawns a new line
	ld	hl, introtext2
	b_call(_PutS)
	b_call(_NewLine)
	b_call(_NewLine)
	ld	hl, introtext3
	b_call(_PutS)
; Wait a few seconds
	b_call(_GetKey)			; waits for any key to be pressed
	b_call(_RunIndicOff)	; turns off top-left animation.
	b_call(_ClrLCDFull)
	b_call(_HomeUp)
; loop construct
	ld hl, (ProgStart - 1)	; read RAM, starting with program
;	read data from memory
readMem:
	inc hl
	ld a, (hl)
	ld (currentbyte), a
	push hl					; we want to increment this value...
;	write data to screen
	call dispByte
; end loop construct
	b_call(_GetCSC)			; get scan code. does not wait for input.
	pop hl					; ... so we preserve it from destruction.
	cp	skClear				; 'a' gets result of compare
	jr z, cleanup			; if zero, clear was pressed. return.
	jp	readMem				; otherwise, move back to loop.
; Fin.
cleanup:
	b_call(_ClrScrnFull)	; clear everything, including text shadow
	b_call(_HomeUp)
	ret


dispByte:
	ld a, (comparebyte)		; comparebyte is the bit mask for and
	ld b, a					; it can't be loaded into 'b' directly
	ld a, (currentbyte)
	and b					; ignores all bits but the set bit.
	and a					; if a is zero, 'z' flag is set.
	jp nz, fillScreen
	jp z, clearScreen		; if the bit is zero, clear the LCD
GrBufCopy:
	b_call(_GrBufCpy)		; copy PlotSScreen to LCD and display
	ld a, (comparebyte)		; load the bitmask
	srl a					; shift the bit over
	ret c					; when done, move to next byte
	ld (comparebyte), a		; put it back.
	jp dispByte
fillScreen:
	ld hl, PlotSScreen
	ld bc, 767
	ld de, PlotSScreen+1
	ld (hl), $FF
	ldir					; copies hl to de, dec bc, inc hl, inc de
	ld a, $D3				; after bc hits zero, send linkport data
	out (0), a
	jp GrBufCopy
clearScreen:
	ld hl, PlotSScreen
	ld de, PlotSScreen+1
	ld (hl), $00
	ld bc, 767
	ldir
	ld a, $D0
	out (0), a
	jp GrBufCopy


introtext1:
	.db	"VIS 40",0
introtext2:
	.db	"1-Pixel Project",0
introtext3:
	.db "Spencer Wohlers",0
currentbyte:
	.db $00
comparebyte:
	.db %10000000

.end
.end