; *******************************************
; * 10Hz - 100KHz D.D.S. FUNCTION GENERATOR *
; *       Microcontroller Source Code       *
; *              Version : 1.0              *
; *         © 1998 George Vastianos         *
; *******************************************

; Note : 
; This version does not support the frequency 
; limits checking, so the LED is always on.

.include "1200def.inc"

	rjmp	RESET	;reset handle

;*****************************************************
;* "BCD2BIN" - BCD to 16-Bit Binary Conversion       *
;*                                                   *
;* This subroutine converts a 6-digit packed BCD     *
;* number represented by 3 bytes (fBCD2:fBCD1:fBCD0) *
;* to a 16-bit number divided by 2 (tbinH:tbinL).    *
;*****************************************************
.def	fBCD0	=r16		;BCD value digits 1 and 0
.def	fBCD1	=r17		;BCD value digits 3 and 2
.def	fBCD2	=r18		;BCD value digits 5 and 4
.def	tbinL	=r19		;Low  byte of binary result (same as mp10L)
.def	tbinH	=r20		;High byte of binary result (same as mp10M)
.def	mp10L	=r19		:Low  byte of number to be multiplied by 10
.def	mp10M	=r20		:Mid  byte of number to be multiplied by 10
.def	mp10H	=r21		;High byte of number to be multiplied by 10
.def	copyL	=r22		;temporary register
.def	copyM	=r23		;temporary register
.def	copyH	=r24		;temporary register
.def	adder	=r25		;value to add after multiplication	
mul10a:	
	swap	adder
mul10b:	
	mov	copyL,mp10L	;make copy
	mov	copyM,mp10M
	mov	copyH,mp10H
	lsl	mp10L		;multiply original by 2
	rol	mp10M
	rol	mp10H
	lsl	copyL		;multiply copy by 2
	rol	copyM
	rol	copyH		
	lsl	copyL		;multiply copy by 2 (4)
	rol	copyM
	rol	copyH		
	lsl	copyL		;multiply copy by 2 (8)
	rol	copyM
	rol	copyH		
	add	mp10L,copyL	;add copy to original
	adc	mp10M,copyM
	adc	mp10H,copyH	
	andi	adder,0x0f	;mask away upper nibble of adder
	add	mp10L,adder	;add lower nibble of adder
	clr	adder	
	adc	mp10M,adder		
	adc	mp10H,adder		
	ret	
BCD2BIN:
	clr	mp10H		
	clr	mp10M		
	mov	adder,fBCD2
	swap	adder
	andi	adder,0x0f	;mask away upper nibble of adder	
	mov	mp10L,adder	;mp10H:mp10M:mp10L = a	
	mov	adder,fBCD2
	rcall	mul10b		;mp10H:mp10M:mp10L = 10a+b
	mov	adder,fBCD1
	rcall	mul10a		;mp10H:mp10M:mp10L = 10(10a+b)+c
	mov	adder,fBCD1
	rcall	mul10b		;mp10H:mp10M:mp10L = 10(10(10a+b)+c)+d
	mov	adder,fBCD0		
	rcall	mul10a		;mp10H:mp10M:mp10L = 10(10(10(10a+b)+c)+d)+e
	mov	adder,fBCD0
	rcall	mul10b		;mp10H:mp10M:mp10L = 10(10(10(10(10a+b)+c)+d)+e)+f
	clc
	ror	mp10H		;Divide result by 2
	ror	mp10M
	ror	mp10L
	ret

;*********************************************
;* "READTWS" - Read Thunpweel Switches       *
;*                                           *
;* This subroutine converts a 6-digit packed *
;* BCD number represented by 3 bytes         *
;* (fBCD2:fBCD1:fBCD0) to a 16-bit number    *
;* divided by 2 (tbinH:tbinL)                *
;*********************************************
.def	fBCD0	=r16		;BCD value digits 1 and 0
.def	fBCD1	=r17		;BCD value digits 3 and 2
.def	fBCD2	=r18		;BCD value digits 5 and 4
.def	thsl	=r19
.def	thrd	=r20	
READTWS:
	clr	fBCD0		;Clear fBCD0
	clr	fBCD1		;Clear fBCD1
	clr	fBCD2		;Clear fBCD2
	in	thsl,PIND	;Read TW1 & TW2
	andi	thsl,0x40
	ori	thsl,0x01
	out	PORTD,thsl
	rcall	delay
	in	thrd,PINB
	andi	thrd,0xf0
	swap	thrd
	or	fBCD0,thrd
	rcall	delay
	in	thsl,PIND
	andi	thsl,0x40
	ori	thsl,0x02
	out	PORTD,thsl
	rcall	delay
	in	thrd,PINB
	andi	thrd,0xf0
	or	fBCD0,thrd
	rcall	delay
	in	thsl,PIND	;Read TW3 & TW4
	andi	thsl,0x40
	ori	thsl,0x04
	out	PORTD,thsl
	rcall	delay
	in	thrd,PINB
	andi	thrd,0xf0
	swap	thrd
	or	fBCD1,thrd
	rcall	delay
	in	thsl,PIND
	andi	thsl,0x40
	ori	thsl,0x08
	out	PORTD,thsl
	rcall	delay
	in	thrd,PINB
	andi	thrd,0xf0
	or	fBCD1,thrd
	rcall	delay
	in	thsl,PIND	;Read TW5 & TW6
	andi	thsl,0x40
	ori	thsl,0x10
	out	PORTD,thsl
	rcall	delay
	in	thrd,PINB
	andi	thrd,0xf0
	swap	thrd
	or	fBCD2,thrd
	rcall	delay
	in	thsl,PIND
	andi	thsl,0x40
	ori	thsl,0x20
	out	PORTD,thsl
	rcall	delay
	in	thrd,PINB
	andi	thrd,0xf0
	or	fBCD2,thrd
	rcall	delay
	ret

;*********************************
;* "delay" - Small Delay Routine *
;*********************************
.def	temp	=r26
.def	temp2	=r27
delay:
	ldi	temp,$ff
	ldi	temp2,$00
lp1:	dec	temp
	cpse	temp,temp2
	rjmp	lp1	
lp2:	ret

;******************************************
;* "SEND2DDS" - Send Data To DDS          *
;*                                        *
;* This subroutine sends the contents of  *
;* the tbinH:tbinL (DDSH:DDSL) to the DDS *
;******************************************
.def	DDSL	=r21
.def	DDSH	=r22
.def	count	=r23
SEND2DDS:
	in	temp,PINB
	andi	temp,0x00
	ori	temp,0x04
	out	PORTB,temp
	rcall	delay
	rcall	delay
	rcall	delay
	ldi	count,0x10
lp3:	in	temp,PINB
	andi	temp,0x04
	ori	temp,0x02
	out	PORTB,temp
	rcall	delay
	rcall	delay
	rcall	delay
	ror	DDSH
	ror	DDSL
	brcs	lp4
	rjmp	lp5
lp4:	in	temp,PINB
	andi	temp,0x06
	ori	temp,0x01
	out	PORTB,temp
	rcall	delay
	rcall	delay
	rcall	delay
	rjmp	lp6
lp5:	in	temp,PINB
	andi	temp,0x06
	out	PORTB,temp
	rcall	delay
	rcall	delay
	rcall	delay
	rjmp	lp6
lp6:	in	temp,PINB
	andi	temp,0x05
	out	PORTB,temp
	rcall	delay
	rcall	delay
	rcall	delay
	dec	count
	ldi	temp,0x00	
	cpse	count,temp
	rjmp	lp3
	rjmp	lp7	
lp7:	in	temp,PINB
	andi	temp,0x00
	out	PORTB,temp
	rcall	delay
	rcall	delay
	rcall	delay
	ret

;****************
;* Main Program *
;****************
RESET:
	ldi	temp,0x0f
	out	DDRB,temp
	ldi	temp,0x00
	out	PORTB,temp
	ldi	temp,0xff
	out	DDRD,temp
	ldi	temp,0x00
	out	PORTD,temp
loop:	rcall	READTWS
	rcall	BCD2BIN
	mov	DDSH,tbinH
	mov	DDSL,tbinL
	rcall	SEND2DDS
	rcall	delay
	rcall	delay
	rcall	delay
	rcall	delay
	rcall	delay
	rcall	delay
	rcall	delay
	rcall	delay
	rcall	delay
	rcall	delay
	rcall	delay
	rcall	delay
	rcall	delay
	rcall	delay
	rcall	delay
	rcall	delay
	rcall	delay
	rcall	delay
	rcall	delay
	rcall	delay
	rcall	delay
	rcall	delay
	rcall	delay
	rcall	delay
	rcall	delay
	rcall	delay
	rcall	delay
	rjmp	loop
;******************
;* End Of Program *
;******************