;***************************************************************************
;* 
;* File Name            : "blink.asm"
;* Title                : EE-281 Lab #1 Starter File
;* Date                 : September 26, 2000
;* Version              : 1.1
;* Target MCU           : AT90S8515
;*
;* DESCRIPTION
;*
;* Minimal program that turns on LEDs on the STK-200 Development Kit
;* when the corresponding button is pressed.
;*
;*************************************************************************** 

.device AT90S8515                       ; Prohibits use of non-implemented instructions; 
.nolist
.include "8515def.inc"
.list
 
	rjmp	RESET                   ; Set up the reset vector.

; Other vector setup really should go here...

RESET:
	ldi 	R16,low(RAMEND)		; Load low byte address of end of RAM into register R16
	out	SPL,R16			; Initialize stack pointer to end of internal RAM
	ldi 	R16,high(RAMEND)	; Load high byte address of end of RAM into register R16	
	out 	SPH, R16		; Initialize high byte of stack pointer to end of internal RAM

SETUP:
	ldi	R16, $00		; All zeros makes
	out	DDRD, R16		;   port D an input
	
	ldi	R16, $FF		; All ones makes
	out	DDRB, R16		;   port B all outputs


LOOP:	in	R16, PIND               ; Read buttons from port D (active low)
	out	PORTB, R16              ; Output value of buttons to port B (active low)
	rjmp	LOOP                    ; Forever