;In Cerebot2, 4 LEDs (LD1, LD2, LD3, and LD4) are connected to PORTE which are named "user LEDs".
;This program Toggles user LEDs (PORTE) in AVR Assembly Language.
;Use AVR Studio IDE to make the hex file.
;For more information see www.microdigitaled.com and www.digilentinc.com
   
.INCLUDE "M64DEF.INC"	;ATmega64 is used by Cerebot2 board

	;initialize SP (Stack Pointer)
	LDI	R20, HIGH(RAMEND)
	OUT	SPH, R20
	LDI	R20, LOW(RAMEND)
	OUT	SPL, R20

	;PE4 to PE7 as outputs (PE4 to PE7 are connected to LD1 to LD4 respectively)
	LDI	R20, 0xF0	
	OUT	DDRE, R20

L1:	LDI	R20, 0xA0
	OUT	PORTE, R20	;PORTE = 1010 0000 B (LD1 = OFF, LD2 = ON, LD3 = OFF, LD4 = ON)
	RCALL	DELAY	;wait 1 second

	LDI	R20, 0x50	
	OUT	PORTE, R20	;PORTE = 0101 0000 B (LD1 = ON, LD2 = OFF, LD3 = ON, LD4 = OFF)
	RCALL	DELAY	;wait 1 second
	RJMP	L1		;jump to L1

;=======================================================================
;The Delay subroutine creates a delay which is 1 second for XTAL = 8MHz.
;=======================================================================
DELAY:
	LDI	R21, 32		;R21 = 32
DL1:LDI	R22, 200	;R22 = 200

DL2:LDI	R23, 250	;R23 = 250
DL3:NOP
	NOP
	DEC	R23			;R23 = R23 - 1
	BRNE	DL3		;if R23 is not equal to zero then go to DL3
	
	DEC R22			;R22 = R22 - 1
	BRNE	DL2		;if R22 is not equal to zero then go to DL2
	
	DEC R21			;R21 = R21 - 1
	BRNE	DL1		;if R21 is not equal to zero then go to DL1
	RET