A83: Help a newbie

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A83: Help a newbie


Hello everyone,
I'm just into asm now, and I was writing this program modeled after one of 
James' tutorials. Basically, this program starts with a pixel in the middle 
of the screen and draws a continuos line (in the direction of keypad 
presses), until the y-equals key is pressed. Then a single dot moves around 
until you press y-equals again, at which point it will draw the line again. 
Also, if the dot is moving around, it will erase any previously drawn 
pixels it encounters. Finally, pressing clear is supposed to clear the 
screen. The dot is supposed to begin moving from that point again. The 
problem I have is that after I press clear, the screen clears, but after 
that nothing moves (you'll see when you run it). It is just a blank screen. 
It's not frozen though. You can still 2nd quit out of it. I'll comment it 
at the points I am unsure of. Could anyone show me what's wrong? Thanks,
Nathan Smith

.NOLIST
#define equ .equ
#define EQU .equ
#define end .end
#include "ti83asm.inc"
#include "tokens.inc"
.LIST
#define left	02h
#define right	01h
#define up	03h
#define down	04h
#define clear	09h
#define yequ	49h
#define enter	05h
.org 9327h
	call _clrLCDFull
	call _grbufclr
	ld b,47
	ld c,32
	ld d,1
	call _IPoint
	call _runIndicOff
;This draws a line
getkey:
	call _getkey
	cp left
	jp z,Left
	cp right
	jp z,Right
	cp up
	jp z,Up
	cp down
	jp z,Down
	cp clear
	call z,clears		;Is this legal? I don't do it down below where i have jp 
z,clears (i just want it to
	cp yequ		;do the instructions in clears and return back to this point in 
the loop
	jp z,getkeya
	cp enter
	jp z,quit
	jp getkey

clears:		;this originally was only the clear lcd and grafbuf, but I was 
attempting to get the pixel
			;to display where it was before it was cleared
	ld h,b
	ld l,c
	ld a,d
	call _clrLCDFull
	call _grbufclr
	ld b,h
	ld c,l
	ld d,a
	call _IPoint

Left:
	dec b
	ld d,1			;Is it necessary to have ld d,1 every time? I don't change it myself
	call _IPoint
	jp getkey

Right:
	inc b
	ld d,1
	call _IPoint
	jp getkey

Up:
	inc c
	ld d,1
	call _IPoint
	jp getkey

Down:
	dec c
	ld d,1
	call _IPoint
	jp getkey
quit:
	call _clrLCDFull
	call _grbufclr
	ld hl,0000h
	ld (pencol),hl
	ld hl,texta
	call _vputs
	ret
;This moves a point around, modeled after James' tutorial: the labels all 
are similar to above, but an "a" is added
getkeya:
	call _getkey
	cp left
	jp z,Lefta
	cp right
	jp z,Righta
	cp up
	jp z,Upa
	cp down
	jp z,Downa
	cp clear
	jp z,clears
	cp yequ
	jp z,getkey
	cp enter
	jp z,quit
	jp getkeya

Lefta:

	ld d,0
	call _IPoint
	dec b
	jp draw

Righta:

	ld d,0
	call _IPoint
	inc b
	jp draw

Upa:

	ld d,0
	call _IPoint
	inc c
	jp draw

Downa:
	ld d,0
	call _IPoint
	dec c
	jp draw
Draw:
	ld d,1
	call _Ipoint
	jp getkeya
texta:
	.db "Draw-Nathan Smith 10-9-99",0


.end
END