Tutorial 10
The Run Indicator

Overview

What is a Run Indicator? Funny you should ask... The Run Indicator is the marker in the upper right corner of the calclulator's display that comes up when the calculator's CPU is busy doing something. Sort of like the light that flashes when your computer's busy. This tutorial will show you how to turn the Run Indicator on and off.

Programming

Let's take the Getkey program that displays the keycode of a key press program (Tutorial 8). When the program is waiting for a key press, it displays a Run Indicator in the corner of the screen. Isn't that thing annoying? Simple solution is to get rid of it.

#define B_CALL(xxxx)	rst 28h \ .dw xxxx
#define B_JUMP(xxxx)	call 50h \ .dw xxxx

_clrlcdfull		=4540h		;The ususal constants and defines, look at the
                             ;New Commands section for more information
_homeup		=4558h
_puts		=450Ah
_putc		=4504h
_getkey		=4972h
_newline		=452Eh
_RunIndicOff	=4570h

	.org	9D95h

	B_CALL(_clrlcdfull)		; clear screen
	B_CALL(_homeup)	; home the cursor
	B_CALL(_RunIndicOff)	; Turning off the Run Indicator
	ld	hl,txt1		; Display the message at the txt1 label
	B_CALL(_puts)
	B_CALL(_getkey)		; Detect key press
	push	af		; Save key press in register a
	B_CALL(_clrlcdfull)		; clear screen again
	B_CALL(_homeup)	; home again
	ld	hl,txt2		; Display msg2
	B_CALL(_puts)		; Display text
	pop	af		; restore reg a
    call    dishex      ; Follow commands at label dishex to find hex key code
	B_CALL(_getkey)		; pause until next key press
	B_CALL(_newline)		; Move cursor to next line
	ret			;Return to TI-OS

dishex:	push	af	; keep copy of value
	and	0F0h		; terminate lower nibble
	rra			; shift nibble right 4
	rra
	rra
	rra
	ld	l,a		; Display the Key's hex code in Str1
	ld	h,0
	ld	de,hexStr
	push	de		; keep for other nibbler
	add	hl,de		; add offset to hexStr address
    ld  a,(hl)      ; find correct ASCII character from string below to
                    ; display hex code of key pressed.
	B_CALL(_putc)		; display character
	pop	de		
	pop	af		
	and	0Fh		; wipeout upper nibble
	ld	l,a
	ld	h,0
	add	hl,de
	ld	a,(hl)
	B_CALL(_putc)
	B_CALL(clrlcdfull)
	ret			; Return to OS	

hexStr 	.db	"0123456789ABCDEF"	;These are the characters used to display the
                                   ;key's hex code
txt1	.db	"Push a key.",0
txt2	.db	"Key code: ",0

.end
END

New Commands

_RunIndicOff - Disables the Run Indicator

Related Commands

There is a ROM call that does exactly the opposite of the _RunIndicOff call, it is _RunIndicOn ( RunIndicOn = 456Dh). To use it, place it at the end of a program to turn the Indicator back on, or put in in the front of the program to make sure it is on.