**********
* Program IO_4 (6811)
*
* Fetches toggle switches and echoes back to LEDs
*
* Note use of branch statement instead of jump
* Note use of pseudo operator EQU to enhance understanding.
* Note use of indexed addressing in reading and writing to the I/O
* box.
*
* Note that indexed addressing will be used for addressing 1000 - 10FF
* in all future programs.
*
* P. H. Anderson, MSU, 12 Sept 91; Checked 12 Sept 91; 19 Jan 93
**********

PSCT		EQU  $C000
DSCT		EQU  $D000
IDSCT		EQU  $D300

REG_BASE	EQU  $1000

PORTB	EQU  $04
PORTC	EQU  $03
DDRC	EQU  $07

	ORG PSCT

	LDY #REG_BASE	* load reg_base
	CLR DDRC,Y	* port c configured as 8-bit input

TOP
	LDAA PORTC,Y	* get switches
	STAA PORTB,Y	* output to LEDs
	BRA TOP