;**********************************************************************
;   This file is a basic code template for assembly code generation   *
;   on the PICmicro PIC16F876A. This file contains the basic code     *
;   building blocks to build upon.                                    *  
;                                                                     *
;   If interrupts are not used all code presented between the ORG     *
;   0x004 directive and the label main can be removed. In addition    *
;   the variable assignments for 'w_temp' and 'status_temp' can       *
;   be removed.                                                       *                         
;                                                                     *
;   Refer to the MPASM User's Guide for additional information on     *
;   features of the assembler (Document DS33014).                     *
;                                                                     *
;   Refer to the respective PICmicro data sheet for additional        *
;   information on the instruction set.                               *
;                                                                     *
;**********************************************************************
;                                                                     *
;    Filename:	    xxx.asm                                           *
;    Date:                                                            *
;    File Version:                                                    *
;                                                                     *
;    Author:                                                          *
;    Company:                                                         *
;                                                                     * 
;                                                                     *
;**********************************************************************
;                                                                     *
;    Files required:                                                  *
;                                                                     *
;                                                                     *
;                                                                     *
;**********************************************************************
;                                                                     *
;    Notes:                                                           *
;                                                                     *
;                                                                     *
;                                                                     *
;                                                                     *
;**********************************************************************


	list		p=16f876A	; list directive to define processor
	#include	<p16f876A.inc>	; processor specific variable definitions
	
	__CONFIG _CP_OFF & _WDT_OFF & _BODEN_OFF & _PWRTE_ON & _HS_OSC & _WRT_OFF & _LVP_OFF & _CPD_OFF

; '__CONFIG' directive is used to embed configuration data within .asm file.
; The lables following the directive are located in the respective .inc file.
; See respective data sheet for additional information on configuration word.






;***** VARIABLE DEFINITIONS
w_temp		EQU	0x71		; variable used for context saving 
status_temp	EQU	0x72		; variable used for context saving
pclath_temp	EQU	0x73		; variable used for context saving			

indications EQU	0x74




;**********************************************************************
	ORG     0x000             ; processor reset vector

	nop			  			; nop required for icd
  	goto    main              ; go to beginning of program


	ORG     0x004             ; interrupt vector location

	movwf   w_temp            ; save off current W register contents
	movf	STATUS,w          ; move status register into W register
	movwf	status_temp       ; save off contents of STATUS register
	movf	PCLATH,w	  ; move pclath register into w register
	movwf	pclath_temp	  ; save off contents of PCLATH register

; isr code can go here or be located as a call subroutine elsewhere

	movf	pclath_temp,w	  ; retrieve copy of PCLATH register
	movwf	PCLATH		  ; restore pre-isr PCLATH register contents
	movf    status_temp,w     ; retrieve copy of STATUS register
	movwf	STATUS            ; restore pre-isr STATUS register contents
	swapf   w_temp,f
	swapf   w_temp,w          ; restore pre-isr W register contents
	retfie                    ; return from interrupt



main

; remaining code goes here
	bcf		STATUS, RP0
	bcf		STATUS, RP1
	clrf	PORTB
	clrf	PORTA
	bsf		STATUS,RP0
	movlw	0x00
	movwf	TRISA
	movwf	TRISB
	
	bcf		STATUS,RP0
	movlw	0xff
	movwf	PORTB
	movwf	PORTA
	
	call USART_initialize
	call USART_Baud_rate_adjust

loop

RS232in 
	bcf		STATUS,RP0
    btfss   PIR1, RCIF       ; are data there? 
    goto    RS232in          ; no, still no data there 
    movfw   RCREG            ; RS232-Register select 
    movwf   indications      ; and into the memory after 'indications' write
	movwf	PORTB
	
	goto loop




USART_initialize 
    BSF      STATUS, RP0       ; Bank1 
    MOVLW    0x24              ; Transmitter:RS232 , BRGH bit is set
    MOVWF    TXSTA             ; 
    BCF      STATUS, RP0       ; Bank 0 
    MOVLW    0x90              ; Enable serial port, 8bit reception , 
    MOVWF    RCSTA             ; continuous receive
	RETURN

USART_Baud_rate_adjust 
    BSF      STATUS, RP0    ; Bank1 
    MOVLW    0x81           ; Set Baud guesses 9,6 KB with Fosc=20MHz
    MOVWF    SPBRG  
	RETURN

	END                       ; directive 'end of program'