;*********************************************************************
;                                                                    *
;     	Tutorial 6 FLASH Persistant Store			     *    
;                                                                    *
;*********************************************************************
;*	TARGET PIC16F877
;*********************************************************************
; 	
;*********************************************************************
;*	@version 	0.1, 27 September 2001
;*	@author		James Caska
;*********************************************************************

	list      p=16F877        
	#include <p16F877.inc>               



FLASH_ADDRH	EQU	.112		;Place in Shared Register Space
FLASH_ADDRL	EQU	.113		;Place in Shared Register Space
FLASH_DATAH	EQU	.114
FLASH_DATAL	EQU	.115

	ORG	.0
	GOTO	INIT
	;==========================================
	;Autogenerated configuration code PIC16F877
	;Config Wiz V0.1, www.virtualbreadboard.com
	;==========================================
	;=========Write to a location in the flash program memory
FLASH.WRITE
	BSF STATUS, RP1 ;
	BCF STATUS, RP0 ; Bank 2
	MOVF FLASH_ADDRH,W
	ANDLW   0x1f        ;keep address within range
	MOVWF EEADRH ; MSByte of Program Address to read
	MOVF FLASH_ADDRL,W
	MOVWF EEADR ; LSByte of Program Address to read
	MOVF FLASH_DATAH,W
	MOVWF EEDATH ; MS Program Memory Value to write
	MOVF FLASH_DATAL,W
	MOVWF EEDATA ; LS Program Memory Value to write
	BSF STATUS, RP0 ; Bank 3
	BSF EECON1, EEPGD ; Point to PROGRAM memory
	BSF EECON1, WREN ; Enable writes
	BCF INTCON, GIE ; Disable Interrupts
FLASH.WRITE.doWrite:
	movlw   0x84        ;enable writes to program flash
	MOVWF EECON1
	movlw   0x55        ;do timed access writes
	MOVWF EECON2
	movlw   0xaa
	MOVWF EECON2
	bsf EECON1,WR   ;begin writing to flash
	NOP         ;processor halts here while writing
	NOP
	BCF STATUS, RP1 ; Bank 0
	BCF STATUS, RP0 
	RETURN
	;=========Read from a location in the flash program memory
FLASH.READ
	BSF STATUS, RP1 ;
	BCF STATUS, RP0 ; Bank 2
	MOVF FLASH_ADDRH,W
	ANDLW   0x1f        ;keep address within range
	MOVWF EEADRH ; MSByte of Program Address to read
	MOVF FLASH_ADDRL,W
	MOVWF EEADR ; LSByte of Program Address to read
	BSF STATUS, RP0 ; Bank 3
	BSF EECON1, EEPGD ; Point to PROGRAM memory
FlashRead:
	movlw   0x80        ;enable reads from program flash
	MOVWF EECON1
	bsf EECON1,RD   ;read from flash
	nop         ;processor waits while reading
	nop
	BCF STATUS, RP0 ; Bank 2
	MOVF EEDATH,W
	MOVWF FLASH_DATAH
	MOVF EEDATA,W
	MOVWF FLASH_DATAL
	BCF STATUS, RP1 ; Bank 0
	RETURN



GetNextSample
	;Get Next Data Sample _/-\_
	BSF	PORTE,0			;Move to the next data	
	NOP			
	BCF	PORTE,0
	RETURN

INIT

	;==========================================
	;Autogenerated configuration code PIC16F877
	;Config Wiz V0.1, www.virtualbreadboard.com
	;==========================================
	;======Begin PORT Configuration
	BSF STATUS, RP0	;PORT TRIS Registers are on page 1
	;======PORT B
	MOVLW   .255	;PORTB Configuration Bits
	MOVWF   TRISB
	;======PORT C
	MOVLW   .0	;PORTC Configuration Bits
	MOVWF   TRISC
	;======PORT D
	MOVLW   .0	;PORTD Configuration Bits
	MOVWF   TRISD
	;======PORT E
	CLRF	PORTE
	MOVLW   .6	;PORTE Configuration Bits
	MOVWF   TRISE
	BCF STATUS, RP0	;Restore Page0


MAIN
	MOVLW	0x18	;Use Page 3 as persistant Store	
	MOVWF	FLASH_ADDRH
	MOVLW	.255
	MOVWF 	FLASH_ADDRL
MAIN.LOOP
	MOVF	PORTB,W
	MOVWF	FLASH_DATAH
	CALL	GetNextSample
	MOVF	PORTB,W
	MOVWF	FLASH_DATAL
	CALL	FLASH.WRITE
	CLRF	FLASH_DATAH	;Clear to ensure read, really does read back the data
	CLRF	FLASH_DATAL
	CALL	FLASH.READ
	MOVF	FLASH_DATAH,W	;6Bits Only - Means PORTC Loops on 64 not 256
	MOVWF	PORTC
	MOVF	FLASH_DATAL,W
	MOVWF	PORTD
	CALL	GetNextSample

	DECFSZ	FLASH_ADDRL,F
	GOTO	MAIN.LOOP
	GOTO	MAIN
	
	END