********
* Program BOUND_1
*
* Scans switches
*
* if in range	00-3F then	01 displayed on discrete LEDs
*		40-7F		02
*		80-BF		04
*		C0-FF		08
*
* Illustrates use of the compare instruction.
*
* P. H. Anderson, MSU, 26 Sept 91; 15 Jan, '93
*********

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

STACKTP 	EQU  $0045
REG_BASE	EQU  $1000

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

	ORG PSCT

* note that BCS and BLO are the same commands

	LDS #STACKTP	* set stack pointer

	LDY #REG_BASE
	CLR DDRC,Y	* port c configured as 8-bit input
SCAN
	LDAA PORTC,Y	* read switches
	CMPA #$40
	BCS OUT_1	* if less than $40
	CMPA #$80
	BCS OUT_2	* if less than $80
	CMPA #$C0
	BCS OUT_4	* if less than $C0
	BRA OUT_8	* otherwise


OUT_1
	LDAA #$01
	STAA PORTB,Y
	BRA SCAN

OUT_2
	LDAA #$02
	STAA PORTB,Y
	BRA SCAN

OUT_4
	LDAA #$04
	STAA PORTB,Y
	BRA SCAN

OUT_8
	LDAA #$08
	STAA PORTB,Y
	BRA SCAN

* The following routine does the same thing

	ORG PSCT+$50

* note that BLS is the same as the combination of BCS and BEQ

	LDS #STACKTP	* set stack pointer

	LDY #REG_BASE
	CLR DDRC,Y	* port c configured as 8-bit input
_SCAN
	LDAA PORTC,Y	* read switches
	CMPA #$3F
	BCS _OUT_1	* if less than or equal to $3F
	BEQ _OUT_1
	CMPA #$7F
	BCS _OUT_2	* if less than than or equal to $7F
	BEQ _OUT_2
	CMPA #$BF
	BCS _OUT_4	* if less than or equal to $BF
	BEQ _OUT_4
	BRA _OUT_8	* otherwise

_OUT_1
	LDAA #$01
	STAA PORTB,Y
	BRA _SCAN

_OUT_2
	LDAA #$02
	STAA PORTB,Y
	BRA _SCAN

_OUT_4
	LDAA #$04
	STAA PORTB,Y
	BRA _SCAN

_OUT_8
	LDAA #$08
	STAA PORTB,Y
	BRA _SCAN