Code:
LIST P=16F676 ; DIRECTIVE TO DEFINE PROCESSOR
;--------------------------------------------------------------------------------------------------------------------------------------
; VARIABLES USED IN BANK 0 (HEX 20-5F), ALSO ACCESSABLE FROM FROM BANK 1 (HEX A0-DF)
EEPROMCOUNT EQU 0X49 ; USED IN THE FIVE-FOLD EEPROM SAVE
EEPROMADDR EQU 0X50 ; USED IN THE FIVE-FOLD EEPROM SAVE
EEPROMDATA EQU 0X51 ; USED IN THE FIVE-FOLD EEPROM SAVE
MAJORITY EQU 0x52 ; USED IN THE EEPROM LOAD SUBROUTINE TO CALCULATE THE RESULT OF THE MAJORITY CHECK
;--------------------------------------------------------------------------------------------------------------------------------------
EEPROM_SAVE_5 BANK1 ; WRITE ONE BYTE FIVE-FOLD INTO PIC INTERNAL EEPROM
MOVLW D'5' ; PREPARE FIVE-FOLD SAVE
MOVWF EEPROMCOUNT ;
EESAVE_5_LOOP BTFSC EECON1,WR ; EACH EEPROM BYTE WRITE CAN TAKE UP TO 6 MILLISECONDS, DID WE FINISH ANY PREVIOUS WRITE ?
GOTO EESAVE_5_LOOP ; NO, NOT YET, WAIT A BIT MORE
MOVF EEPROMADDR,W ; YES, MAKE SURE THE EEPROM ADDRESS AND DATA BYTES HOLD THE RIGHT VALUE,
MOVWF EEADR ; THE STATUS OF THESE BYTES AFTER A WRITE IS UNKNOWN (AND UNDOCUMENTED)
MOVF EEPROMDATA,W ;
MOVWF EEDATA ;
BSF EECON1,WREN ; ENABLE EEPROM WRITES
; BCF INTCON,GIE ; DISABLE INTERRUPTS < ARE ALREADY DISABLED >
MOVLW H'55' ; WRITE UNLOCK CODE 1
MOVWF EECON2 ; UNLOCK WRITE
MOVLW H'AA' ; WRITE UNLOCK CODE 2
MOVWF EECON2 ; UNLOCK WRITE
BSF EECON1,WR ; ACTIVATE WRITE
BCF EECON1,WREN ; DISABLE EEPROM WRITES
; BSF INTCON,GIE ; RE-ENABLE INTERRUPTS < WILL BE ENABLED ELSEWHERE >
INCF EEPROMADDR,F ; SELECT NEXT WRITE ADDRESS
DECFSZ EEPROMCOUNT,F ; DID WE WRITE ALL FIVE BYTES ?
GOTO EESAVE_5_LOOP ; NO, GO WRITE NEXT BYTE
RETURN ; DONE
;--------------------------------------------------------------------------------------------------------------------------------------
EEPROM_READ ; THE VALUES ARE STORED IN PIC INTERNAL EEPROM. DUE TO POWER FAILURE DURING SAVES OR DUE TO
; OTHER CAUSES THE STORED VALUES MAY BECOME ERRORNOUS. TO MAKE SURE WE GET THE RIGHT VALUES
; WE STORE THEM IN FIVE-FOLD. USING A MAJORITY CHECK WE CAN CIRCUMVENT FALSE BYTES.
; WE WANT AT LEAST THREE OUT OF FIVE (MAJORITY CHECK):
; TRUTH TABLE: KARNAUGH MAP:
;
; EDCBA Y DE DE DE DE
; 0 00000 0 CBA 00 01 10 11
; 1 00001 0
; 2 00010 0 000 0 0 0 0
; 3 00011 0 001 0 0 0 1
; 4 00100 0 010 0 0 0 1
; 5 00101 0 011 0 1 1 1
; 6 00110 0 100 0 0 0 1
; 7 00111 1 101 0 1 1 1
; 8 01000 0 110 0 1 1 1
; 9 01001 0 111 1 1 1 1
; 10 01010 0
; 11 01011 1
; 12 01100 0
; 13 01101 1
; 14 01110 1
; 15 01111 1
; 16 10000 0
; 17 10001 0 BOOLEAN EQUATIONS:
; 18 10010 0
; 19 10011 1 RESULT = A AND B AND C
; 20 10100 0 OR
; 21 10101 1 (A OR B OR C) AND D AND E
; 22 10110 1 OR
; 23 10111 1 (A OR B) AND NOT(A XOR B XOR C) AND (D OR E)
; 24 11000 0
; 25 11001 1
; 26 11010 1
; 27 11011 1
; 28 11100 1
; 29 11101 1
; 30 11110 1
; 31 11111 1
BANK1 ; READ BYTE FROM PIC INTERNAL EEPROM, USE MAJORITY CHECK ONE THE FIVE-FOLD VALUE
BSF EECON1,RD ; PERFORM THE EEPROM READ OPERATION, CURRENT ADDRESS: A
BTFSC EECON1,RD ; MAKE SURE THE READ HAS FINISHED, SEEMS TO BE A PROBLEM ON SOME PIC'S
GOTO $-1 ;
COMF EEDATA,W ; W = NOT(A)
INCF EEADR,F ; SELECT NEXT READ ADDRESS: B
BSF EECON1,RD ; PERFORM THE EEPROM READ OPERATION
BTFSC EECON1,RD ;
GOTO $-1 ;
XORWF EEDATA,W ; W = NOT(A XOR B)
INCF EEADR,F ; NEXT ADDRESS: C
BSF EECON1,RD ;
BTFSC EECON1,RD ;
GOTO $-1 ;
XORWF EEDATA,W ; W = NOT(A XOR B XOR C)
MOVWF MAJORITY ; R = NOT(A XOR B XOR C)
INCF EEADR,F ; NEXT ADDRESS: D
BSF EECON1,RD ;
BTFSC EECON1,RD ;
GOTO $-1 ;
MOVF EEDATA,W ; W = D
INCF EEADR,F ; NEXT ADDRESS: E
BSF EECON1,RD ;
BTFSC EECON1,RD ;
GOTO $-1 ;
IORWF EEDATA,W ; W = D OR E
ANDWF MAJORITY,F ; R = (D OR E) AND NOT(A XOR B XOR C)
MOVLW D'4' ;
SUBWF EEADR,F ; NEXT ADDRESS: A
BSF EECON1,RD ;
BTFSC EECON1,RD ;
GOTO $-1 ;
MOVF EEDATA,W ; W = A
INCF EEADR,F ; NEXT ADDRESS: B
BSF EECON1,RD ;
BTFSC EECON1,RD ;
GOTO $-1 ;
IORWF EEDATA,W ; W = A OR B
ANDWF MAJORITY,F ; R = (A OR B) AND (D OR E) AND NOT(A XOR B XOR C)
DECF EEADR,F ; NEXT ADDRESS: A
BSF EECON1,RD ;
BTFSC EECON1,RD ;
GOTO $-1 ;
MOVF EEDATA,W ; W = A
INCF EEADR,F ; NEXT ADDRESS: B
BSF EECON1,RD ;
BTFSC EECON1,RD ;
GOTO $-1 ;
IORWF EEDATA,W ; W = A OR B
INCF EEADR,F ; NEXT ADDRESS: C
BSF EECON1,RD ;
BTFSC EECON1,RD ;
GOTO $-1 ;
IORWF EEDATA,W ; W = A OR B OR C
INCF EEADR,F ; NEXT ADDRESS: D
BSF EECON1,RD ;
BTFSC EECON1,RD ;
GOTO $-1 ;
ANDWF EEDATA,W ; W = (A OR B OR C) AND D
INCF EEADR,F ; NEXT ADDRESS: E
BSF EECON1,RD ;
BTFSC EECON1,RD ;
GOTO $-1 ;
ANDWF EEDATA,W ; W = (A OR B OR C) AND D AND E
IORWF MAJORITY,F ; R = ((A OR B OR C) AND D AND E) OR ((D OR E) AND NOT(A XOR B XOR C))
MOVLW D'4' ;
SUBWF EEADR,F ; NEXT ADDRESS: A
BSF EECON1,RD ;
BTFSC EECON1,RD ;
GOTO $-1 ;
MOVF EEDATA,W ; W = A
INCF EEADR,F ; NEXT ADDRESS: B
BSF EECON1,RD ;
BTFSC EECON1,RD ;
GOTO $-1 ;
ANDWF EEDATA,W ; W = A AND B
INCF EEADR,F ; NEXT ADDRESS: C
BSF EECON1,RD ;
BTFSC EECON1,RD ;
GOTO $-1 ;
ANDWF EEDATA,W ; W = A AND B AND C
IORWF MAJORITY,W ; W = (A AND B AND C) OR ((A OR B OR C) AND D AND E) OR ((D OR E) AND NOT(A XOR B XOR C))
RETURN ; DONE, RETURN WITH VALUE IN W REGISTER
;--------------------------------------------------------------------------------------------------------------------------------------
+
| file: /Techref/member/AT-planet-T9/safeeeprom.htm, 11KB, , updated: 2010/10/1 20:10, local time: 2024/12/27 06:40,
owner: AT-planet-T9,
13.59.36.4:LOG IN
|
| ©2024 These pages are served without commercial sponsorship. (No popup ads, etc...).Bandwidth abuse increases hosting cost forcing sponsorship or shutdown. This server aggressively defends against automated copying for any reason including offline viewing, duplication, etc... Please respect this requirement and DO NOT RIP THIS SITE. Questions? <A HREF="http://ecomorder.com/Techref/member/AT-planet-T9/safeeeprom.htm"> EEPROM write with majority check for PIC 16F676</A> |
| Did you find what you needed? |