;**********************************************************************
;   This file is a basic code template for assembly code generation   *
;   on the PIC16F628A. This file contains the basic code              *
;   building blocks to build upon.                                    *
;                                                                     *
;   Refer to the MPASM User's Guide for additional information on     *
;   features of the assembler (Document DS33014).                     *
;                                                                     *
;   Refer to the respective PIC data sheet for additional             *
;   information on the instruction set.                               *
;                                                                     *
;**********************************************************************
;                                                                     *
;    Filename:	    xxx.asm                                           *
;    Date:                                                            *
;    File Version:                                                    *
;                                                                     *
;    Author:                                                          *
;    Company:                                                         *
;                                                                     *
;                                                                     *
;**********************************************************************
;                                                                     *
;    Files Required: P16F628A.INC                                     *
;                                                                     *
;**********************************************************************
;                                                                     *
;    Notes:                                                           *
;                                                                     *
;**********************************************************************

	list      p=16f628A           ; list directive to define processor
	#include <p16F628A.inc>       ; processor specific variable definitions

	#define LED		PORTA,4
	#define Bank0	bcf STATUS,RP0	
	#define Bank1	bsf STATUS,RP0

	errorlevel  -302              ; suppress message 302 from list file

	__CONFIG   _CP_OFF & DATA_CP_OFF & _LVP_ON & _BOREN_OFF & _MCLRE_ON & _WDT_OFF & _PWRTE_OFF & _HS_OSC 

;***** VARIABLE DEFINITIONS

w_temp        EQU     0x7E        ; variable used for context saving 
status_temp   EQU     0x7F        ; variable used for context saving

;**********************************************************************

	ORG     0x000             ; processor reset vector
	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

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

	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

	; port inits
	clrf	PORTA		; zero ports A et B
	clrf	PORTB
	movlw	0x07
	movwf	CMCON		; set port A mode I/O digital
	bcf		STATUS,RP1
	Bank1
	clrf	TRISB		; port B is OUT
	bsf		TRISB,1 	; RX is IN
	clrf	TRISA 		; port A is OUT
	Bank0

	; USART config
	Bank1
	movlw	0x09 		; value for the BRG
	movwf	SPBRG 		; init BRG 31250 bauds
	bcf		TXSTA,SYNC
	Bank0
	bsf		RCSTA,SPEN	; start the USART rx/tx
	bsf		RCSTA,CREN	; both line can be resume in one here

MainLoop
	bsf		LED			; LED-

WaitMidi
	btfss	PIR1,RCIF	; wait for RX flag
	goto	WaitMidi	; loop until a byte is received

	bcf		LED			; LED+
	movf	RCREG,W		; read the USART register (the MIDI byte is now avalable in W register for future use)
	movwf	TXREG		; write W to the USART register

	goto 	MainLoop

; initialize eeprom locations

	ORG	0x2100
	DE	0x00, 0x01, 0x02, 0x03

	END                       ; directive 'end of program'