Title "RS_PWM.asm"
        list p=16c74,f=inhx8m

;This program runs on the PICDEM-2 demo board.
;In the Demo board, Port B is connected to 8 LEDs. 
;When the PIC16C74 receives a word of data from
;the USART, the value is displayed on the LEDs and
;is retransmitted to the host computer.


STATUS  equ     03H		;Status Register
PCL	equ	02H
PORTB 	equ     06H		;PORTB Data Latch when written PORTB pins when read PORTB = 8 Bit wide bi-directional port
TRISB   equ     06H
PORTC   equ     07H
TRISC   equ     07H
TMR2	equ	11H
PR2	equ	92H
CCP1CON	equ	17H
CCP2CON	equ	1DH
CCPR1L	equ	15H
CCPR2L	equ	1BH
T2CON	equ	12H

CASE	equ	21H
TEMP_X	equ	22H

INTCON  equ     0BH		;Interrupt ... Register
PIE1    equ     0CH		;Contains individual enable bits for the Peripheral Interrupt Register
PIR1    equ     0CH		;Contains individual flag bits for the Peripheral Interrupt Register
TXSTA   equ     18H		;Transmit Status and Control Register
				;Bit 2 of TXSTA = BRGH (Baud Rate Generator High Speed)
				;Equations: 
				;Bit 2: BRGH = 0 (Low Speed)
				;Bit 4: SYNC = 0 (Asynchronous) Desired Baud Rate = Fosc (4 MHz)/64(X+1) (For 9600 X=5.51 --> Calculated Baud Rate w/ X=6 --> 8929 = 7 % Error)
				;Bit 4: SYNC = 1 (Synchronous) Desired Baud Rate = Fosc (4 MHz)/4(X+1)
				;Bit 2: BRGH = 1 (High Speed); SYNC = 0 Desired Baud Rate = Fosc (4 MHz)/16(X+1) (For 9600 X=25.042 --> Calculated Baud Rate w/ X=25 --> 9615 = 0.16 % Error)
				;X = SPBRG Value (decimal) (For 2404 Baud --> X = 103)
RCSTA   equ     18H		;Receive Status and Control Register
TXREG   equ     19H		;USART Transmit Data Register (USART = Universal Synchronous Asynchronous Receiver Transmitter)
SPBRG   equ     19H		;Baud Rate Generator Register
RCREG   equ     1AH		;USART Receive Data Register
PIR1    equ     0CH		;-Doppelt deklariert??
COUNT   equ     0x20
Z       equ     2h
RP0     equ     5h		;Register Bank Select Bits (used for direct adressing)


	org	00h		;Reset Vector
	goto	Start		;Unconditional Branch to Start; PC = Address Start

	org	04h
	goto	IntVector

        org     05h		;Beginning of program EPROM

Init
	bcf	STATUS,RP0	;Status[RP0]=1
	clrf    PORTC


	bsf	STATUS,RP0	;Status[RP0]=1
	clrf	TRISC
	
	bcf	STATUS,RP0	;Status[RP0]=1
        clrf    PORTB           ;Clear PORTB output latches
				;Z=1
	bsf	STATUS,RP0	;Status[RP0]=1
	clrf    TRISB		;Config PORTB as all outputs
				;Z=1
	movlw	b'00100000'	;Move 8 Bits into W; Enable RCIF interrupt
	movwf	PIE1		;Move W into PIE1 --> RCIE=1 Enables the USART receive interrupt
	movlw	18h		;Move 18h into W; 9600 baud @4MHz

	movwf	SPBRG		;Move W(==18h) into SPBRG --> Baud Rate Generator Register = 29h == 9600 Baud

	movlw	b'10100100'	;Move 8 Bits into W; Async, High baud rate
        movwf	TXSTA		;Move W into TXSTA
				;TXSTA[7]= CSRC (Clock Source Bit);	 		1 == Don't care (W/ SYNC == 1 --> 1 == Master mode (Clock internally from BRG))
				;TXSTA[6]= TX9 (9 bit Transmit Enable Bit)		0 == Select 8 bit tranmissions
				;TXSTA[5]= TXEN (Transmit Enable Bit); 			1 == Transmit enabled
				;TXSTA[4]= SYNC (USART Mode Serlect Bit);		0 == Asynchronous mode
				;TXSTA[3]= Unimplemented (Read as 0)
				;TXSTA[2]= BRGH (High Baud Rate Select Bit);		1 == (w/ SYNC = 0) 1 == High Speed
				;TXSTA[1]= TRMT (Transmit Shift Register Status Bit);	0 == TSR full
				;TXSTA[0]= TX9D (9th Bit of transmit data. Can be parity bit)

	bcf	STATUS,RP0	;STATUS[RP0]= 0; 0 == Register Bank 0 selected (00h - 7fh)
	
	movlw	b'10010000'	;Move 8 Bit into W; Enable continous reception
	movwf	RCSTA		;Move W into RCSTA
				;RCSTA[7]= SPEN (Serial Port Enable Bit); 		1 == Serial Port enabled
				;RCSTA[6]= RX9 (9 bit Receive Enable Bit)		0 == Select 8 bit reception
				;RCSTA[5]= SREN (Single Receive Enable Bit);		0 == (w/ SYNC = 0) Don't care
				;RCSTA[4]= CREN (Continous Receive Bit);		1 == (w/ SYNC = 0) Enables continous receive
				;RCSTA[3]= Unimplemented (Read as 0)
				;RCSTA[2]= FERR (Framing Error Bit);			0 == no error (1 == Framing Error --> Can be updated by reading RCREG register)
				;RCSTA[1]= OERR (Overrun Error Bit);			0 == no overrun error ( 1 == Overrun error --> Can be cleared by clearing bit CREN)
				;RCSTA[0]= RX9D (9th Bit of received data. Can be parity bit)

	movlw	b'11000000'	;Move 8 Bit into W; Enable global interrupts
	movwf	INTCON		;Move W into INTCON
				;INTCON[7]= GIE (Global Interrupt Enable Bit);		1 == Enables all un-masked interrupts
				;INTCON[6]= PEIE (Peripheral Interrupt Enable Bit);	1 == Enables all un-masked peripheral interrupts
				;INTCON[5]= TOIE (TMRO Overflow Interrupt Enable Bit);  0 == Disables the TMRO Interrupt
				;INTCON[4]= INTE (RBO/INT External Interrupt Enable Bit)0 == Disables the the RBO/INT external interrupt
				;INTCON[3]= RBIE (RB Port Change interrupt Enable Bit);	0 == Disabled
				;INTCON[2]= TOIF (TMRO Overflow Interrupt Flag);	0 == no overflow
				;INTCON[1]= INTF (RBO/INT External Interrupt Flag Bit); 0 == no RB=/INT Ext. Interrupt did occur
				;INTCON[0]= RBIF (RB Port Change Interrupt Flag Bit);	0 == None of the RB7:RB4 pins have changed state


	bsf	STATUS,RP0	; Umschaltung auf Bank 

	movlw	B'10000000'	; Port C Bit 0,1 als Ausgabe (PWM)
	movwf	TRISC		; Port C Bit 7 als Eingabe (C0=Zustand)

	movlw	B'11111111'
	movwf	PR2		; PR2 Register f黵 PWM setzen

	bcf	STATUS,RP0	; Umschaltung auf Bank 0
	clrf 	CCP1CON
	nop

	movlw	0x0c
	movwf	CCP1CON		; als PWM initialisieren

	clrf 	CCP2CON
	nop
	movlw	0x0c
	movwf	CCP2CON		; als PWM initialisieren

	movlw	B'00000100'


	movwf	T2CON		; Initialisierung und Einschalten von Timer2

	bsf STATUS,RP0
	movlw	B'10000000'
	movwf	TRISC
	bcf	STATUS,RP0	; Umschaltung auf Bank 0	
	return

	return
;end of Init


IntVector
Loop1
	movlw	06h		;Mask out unwanted bits; 8 bit Literal (06h) is loaded into W register
	andwf	RCSTA,W		;Check for errors; And W w/ RCSTA: If W==0 then W=result else RCSTA=result; Status affected Z
	btfss	STATUS,2	;Zero Bit test, skip if set
				;Zero Bit=1 when result==0; Zero Bit=0 when result=!0
				;Status[2]==1 ? next line: NOP instead of next line
	goto	RcvError	;Found error, flag it
	
	btfss	PIR1,5		;RCIF Bit test, skip if zero; Check for data ready
				;Bit 5 = RCIF = Serial communication interface receive interrupt flag
				;1 = Receive buffer is full
				;0 = Receive buffer is empty
	retfie			;Return from interrupt
				;Some other interrupt, exit
	
	btfss	CASE,0
	goto 	Else_
	goto	Case1

Else_	
	bsf	CASE,0
	movf	RCREG,W		;Get input data
	movwf	TEMP_X		;Move data into Temp_X
	goto	Case_end
Case1	
	bcf	CASE,0
	movf	RCREG,W		;Get input data
	movwf	CCPR2L		;Value into PWM2 - register
	movf	TEMP_X,0	;Move Temp_X into W register
	movwf	CCPR1L	
	goto	Case_end

Case_end			
	goto Loop1
	retfie			;Return from interrupt
;end of InitVector


RcvError
	bcf	RCSTA,4		;Clear reciever status; RCSTA[4]=0
	bsf	RCSTA,4		;RCSTA[4]=1

	movlw	0FFh		;Light all LEDs
	movwf	PORTB	
	
	retfie			;Return from interrupt
;end of RcvError


Start	call Init

Loop	
	goto	Loop		;Unconditional Branch to Loop; PC = Address Loop

	end