ORG	$C000
INPUT	EQU $FFAC
OUTPORT	EQU $1004	;output port : Chip -> D/A : This is port B
CTLPORT	EQU	$1003	;I/O Port : Control D/A and A/D : This is port C
DDRC	EQU	$1007	;data direction register for port C
INPORT	EQU	$100A	;input port  : A/D -> Chip : This is port E
MYDATA	EQU 	$D000	;location of data
NUMSMP	EQU	#100	;number of samples being taken

	ORG	$C100
	LDAA	#$F7
	STAA	DDRC	;this sets all port C pins to output except pin 3, which is A/D
"busy"
	LDAA	#$C0
	STAA	CTLPORT	;initialize the control port so nothing is happening
	
START
	LDAA	#$C0
	STAA	CTLPORT	;initialize the control port so nothing is happening
LOOP1	JSR	INPUT	;listen to keyboard for start
      	TSTA		;see if there is a key pressed
      	BEQ LOOP1	;if not, loop to start	
       	CMPA #$58	;check for capital X
       	BEQ GETDATA	   
       	CMPA #$78	;check for lowercase x
       	BEQ GETDATA	
       	CMPA #$52	;check for capital R
       	BEQ SENDREV	   
       	CMPA #$72	;check for lowercase r
       	BEQ SENDREV
       	CMPA #$50	;check for capital P
       	BEQ SENDPLAY	   
       	CMPA #$70	;check for lowercase p
       	BEQ SENDPLAY		
       	CMPA #$20	;check for space
       	BEQ FINISH			
		BRA	LOOP1	;branch back to start if the input isn't one we want

GOTOSTART	BRA	START

GETDATA
*start the conversion
	LDAA	#$C7	;set start conversion bit, RD, and CS high - keep D/A off
	STAA	CTLPORT	;set the control register
*set up the loop variable	
	LDAB	NUMSMP	;this will be used as a counter
	DECB			;this is here becuase to adjust the loop
	LDX		MYDATA	;the start location for the data
GETLOOP	LDAA	CTLPORT	;get current control status
*check to see if A/D is busy	
	ANDA	#$08	;AND with 8 to get nothing but the "busy" signal bit
	CMPA	#$08	;if true, then the busy signal is on
	BEQ		GETLOOP	;if busy, keep waiting (branch to start of loop again)
*if not busy... 
	LDAA	#$C1	;set RD and CS to low so we can read data  - keep D/A off
	STAA	CTLPORT
*the port is now ready to be read
	LDAA	INPORT	;get the data from the port
	STAA	$X		;store it in the data location
	INX				;increment X so we can store the next value
*reset port so it starts conversion again
	LDAA	#$C7	;set start conversion bit, RD, and CS high - keep D/A off
	STAA	CTLPORT	;set the control register
	DECB			;decrement the counter
	TSTB
	BEQ START		;if counter is 0, all data is collected, go to start and wait
	BRA	GETLOOP		;if counter is not 0, keep getting data
	
SENDPLAY
	LDAA	#$00	
	STAA	CTLPORT	;initialize the control port so D/A is running
	LDAB	NUMSMP	;this will be used as a counter
	DECB			;this is here becuase to adjust the loop
	LDX		MYDATA	;the start location for the data	
SPLOOP	LDAA	$X	;load data at location stored in register X
	STAA	OUTPORT	;write data to D/A converter
	INX				;increment X
	DECB			;decrement counter
	TSTB
	BEQ START		;if counter is 0, all data is collected, go to start and wait
	BRA	SPLOOP		;if counter is not 0, keep getting data

SENDREV
	LDAA	#$00	
	STAA	CTLPORT	;initialize the control port so D/A is running
	LDD		MYDATA	;the start location for the data
	ADDD	NUMSMP	;since we're working backwards, add number of samples
	STD		$X		;store in X
	DEX				;then decrement X to point at the last data point
	LDAB	NUMSMP	;this will be used as a counter
	DECB			;this is here becuase to adjust the loop
	
SRLOOP	LDAA	$X	;load data at location stored in register X
	STAA	OUTPORT	;write data to D/A converter
	DEX				;increment X
	DECB			;decrement counter
	TSTB
	BEQ GOTOSTART		;if counter is 0, all data is collected, go to start and wait
	BRA	SRLOOP		;if counter is not 0, keep getting data

FINISH	RTS
       	END