**********************************************************************
*	Example 1a
**********************************************************************

* Version 1.00a, written by Kenrick Chin, 1999 Jun 24
* Demonstrates how to toggle PD5 output
* using indexed addressing mode for I/O addresses
* and BSET/BCLR to set and clear individual bits

*---------------------------------------------------------------------
* Define hardware constants
*---------------------------------------------------------------------

EEPROM	EQU	$F800		;start of EEPROM
REGS	EQU	$1000		;I/O bas address
PORTD	EQU	$08		;offset address of portD
DDRD	EQU	$09		;offset for portD Data Direction Reg
PD5	EQU	%00100000	;bit mask for PD5

**********************************************************************
*	CODE SEGMENT
**********************************************************************

	ORG	EEPROM

start	LDX	#REGS		;setup I/O base address
	BSET	DDRD,X PD5	;set PD5 for output

main	BSET	PORTD,X PD5	;send high signal on PD5
	BCLR	PORTD,X PD5	;and set it low again
	BRA	main		;loop forever

**********************************************************************
*	Interrupt Vectors
**********************************************************************

	ORG	$FFFE
	FDB	start		;reset vector
	END