******
* Program BOUND_2
*
* Displays distance between first two occurances of
* data pattern specified using toggle switches.
*
* Scans mem range F000 - F0FF
*
* If no match found outputs 00
* if no second match outputs FF
*
* Illustrates use of cmp op to test equality.
*
* Peter Anderson, 1 Oct 91; 15 Jan, '93
******

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

STACKTP 	EQU  $0045
REG_BASE	EQU  $1000

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

	ORG PSCT

	LDS #STACKTP
	LDY #REG_BASE

	CLR DDRC,Y	* port c configured as 8-bit input

	LDX FIRST_LOC	* set to first location

	LDAA PORTC,Y	* get switches
	STAA PATT	* and save in patt

	CLR DISTANCE	* zero the distance

	CLR PORTB,Y	* zero the LEDs

TEST_EQ
	LDAA 00,X	* get mem data
	CMPA PATT
	BEQ FIRST_M	* if match

	INX		* next mem location
	CPX LAST_LOC	* done?
	BCS TEST_EQ
	BEQ TEST_EQ
* else there was no match
NO_MATCH
	CLR PORTB,Y	* output 00, no match found
	SWI		* halt

FIRST_M 		
* 			* first match

	INC DISTANCE	* distance
	INX		* next mem loc
	CPX LAST_LOC	* done?
	BEQ L1
 	BCC NO_2_MATCH
L1
	LDAA 00,X	* get data
	CMPA PATT	* same as pattern
	BNE FIRST_M

SECOND_M
	LDAA DISTANCE	* if second match
	STAA PORTB,Y	* output distance
	SWI

NO_2_MATCH
	LDAA #$FF	* output FF
	STAA PORTB,Y
	SWI

	ORG IDSCT

FIRST_LOC	EQU  $F000
LAST_LOC	EQU  $F0FF


	ORG DSCT

PATT		RMB 1
DISTANCE	RMB 1