/****
 * GPIO_Output.asm
 *
 *  Modified: 29 Jan 2026
 *  Author: Dr. Schwartz
 
 This program shows how to initialize a GPIO port on the Atmel 
 (Port D for this example) and demonstrates various ways to write to 
 a GPIO port.  The output will blink LEDs at the bottom left of the 
 uPAD, labeled D4. PortD4, PortD5, and PortD6 are the red, green, 
 and blue LEDs, respectively.  Note that these LEDs are active-low.
****/

;Definitions for all the registers in the processor. ALWAYS REQUIRED.
;View the contents of this file in the Processor "Solution Explorer" 
;   window under "Dependencies"
.include "ATxmega128A1Udef.inc"

; some definitions, pre-defined
.equ	BIT4 = 0b00010000
.equ	INV4 = 0b11101111
.equ	RED = INV4
.equ	BIT5 = 0b00100000
.equ	INV5 = ~BIT5
.equ	GREEN = ~(BIT5)
.equ	BIT6 = 0x40
.equ	BLUE = ~(BIT6)
.equ	BIT456 = 0x70
.equ	WHITE = ~(BIT456)
.equ	BIT64 = 0x50
.equ	PINK = ~(BIT64)
.equ	BLACK = 0xFF

.ORG 0
;Skip address through 0x00FD (interrupt vectors)
	rjmp MAIN

;Start program at 0x0100 so we don't overwrite vectors (0-0x00FD)
.ORG 0x0100	
MAIN:
; initialize the data direction of the three LEDs as outputs (PD4-6)
	ldi r16, BIT456
	sts PORTD_DIRSET, r16

; Turn on the red LED (only)
	ldi r16, RED
	sts PORTD_OUT, r16
		
; Turn on the green LED (only)
	ldi r16, GREEN
	sts PORTD_OUT, r16

; Turn on the blue LED (only)
	ldi r16, BLUE
	sts PORTD_OUT, r16
	
; Turn on all of the colored LEDs to make white
	ldi r16, WHITE
	sts PORTD_OUT, r16

; Turn on blue and red to make a pink (magenta)
	ldi r16, PINK
	sts PORTD_OUT, r16
	
; Turn off all of the LEDs (i.e., make it black)
	ldi r16, BLACK
	sts PORTD_OUT, r16

; Turn on the blue LED (only, i.e., make BIT6 0 using OUTCLR)
	ldi r16, BIT6
	sts PORTD_OUTCLR, r16

; Turn off the blue LED (i.e., make BIT6 a 1, using OUTSET)
	ldi r16, BIT6
	sts PORTD_OUTSET, r16

; Make an endless loop (repeat forever) and TOGGLE the blue LED.
;  (use OUTTGL)  
REPEAT:
	sts PORTD_OUTTGL, r16
	rjmp REPEAT