You may try this comparing to your program
                ;void weprom(char adr, char value)
                        ;{ EEADR=adr; EEDATA=value; EEPGD = 0; WREN = 1; GIE=0; EECON2 = 0x55;
EECON2=0xAA;  WR=1; GIE=1;
weprom:
        BCF   0x03,RP0
        BCF   0x03,RP1
        MOVWF value             ;save parameters only... not important for you
        MOVF  adr_2,W
        BSF   0x03,RP1
        MOVWF EEADR
        BCF   0x03,RP1
        MOVF  value,W
        BSF   0x03,RP1
        MOVWF EEDATA
        BSF   0x03,RP0
        BCF   0x18C,EEPGD
        BSF   0x18C,WREN
        BCF   0x0B,GIE
        MOVLW .85
        MOVWF EECON2
        MOVLW .170
        MOVWF EECON2
        BSF   0x18C,WR
        BSF   0x0B,GIE
                        ;  while (WR);
m039    BSF   0x03,RP0
        BSF   0x03,RP1
        BTFSC 0x18C,WR
        GOTO  m039
        BSF   0x03,RP0  ;WREN=0;
        BSF   0x03,RP1
        BCF   0x18C,WREN
                        ;}
        RETURN

                        ;char leprom (char adr)
                        ;{ EEADR=adr; EEPGD=0; RD=1; return EEDATA; }
leprom
        BCF   0x03,RP0
        BCF   0x03,RP1
        MOVWF adr        :save parameters as above
        MOVF  adr,W
        BSF   0x03,RP1
        MOVWF EEADR
        BSF   0x03,RP0
        BCF   0x18C,EEPGD
        BSF   0x18C,RD
        BCF   0x03,RP0
        MOVF  EEDATA,W
        RETURN

It's written in C and not very optimized.
Hope it helps you a little.

Igor


-----Original Message-----
From: pic microcontroller discussion list
[mailto:PICLIST@MITVMA.MIT.EDU]On Behalf Of Jai Dhar
Sent: 19. ledna 2003 21:24
To: PICLIST@MITVMA.MIT.EDU
Subject: [PIC]: EEPROM on f877


Hi,

I'm having a wierd problem writing/reading to the EEPROM on the f877. I
wanted
to make two routines to write and read, and this is what I came up with:

;Writes the value in W to the address in 'temp'
EEPROMWrite

 bsf STATUS,RP1   ;Switch to bank 2
 movwf EEDATA
 bcf STATUS,RP1   ;Back to Bank 0
 movf temp,w
 bsf STATUS,RP1   ;And back again to Bank2
 movwf EEADR

 ;Set to Bank 3
 bsf STATUS,RP0
 ;Enable EEPROM Writing
 bsf EECON1,WREN

 movlw 0x55
 movwf EECON2
 movlw 0xAA
 movwf EECON2
 ;Begin Write
 bsf EECON1,WR
 bcf EECON1,WREN

 ;Switch back to Bank 0

 bcf STATUS,RP0
 bcf STATUS,RP1

retlw 0x00

;Reads the value at address W and puts it back in temp
EEPROMRead

 ;Switch to bank 2
 bsf STATUS,RP1
 ;Move the address in W to EEADR
 movwf EEADR
 ;Switch to bank 3
 bsf STATUS,RP0
 ;Start the reading
 bsf EECON1, RD
 ;Back to Bank 2
 bcf STATUS,RP0
 movf EEDATA,w

 ;Switch bank to Bank 0
 bcf STATUS,RP1
 bcf STATUS,RP0
 ;Move the contents of W to temp
 movwf temp

retlw 0x00

Now what's wierd is that I called the Write fn twice, two different values,
different addresses... and then called read on one of them. I read it
fine...
I then rewrote the code to read the other address (just one at atime), and I
got the same thing?? So I'm not sure which fn. is working incorrectly.

Anything seem to be wrong with my code? I know it's probably a bit
inefficient, but I just want to get it working first. If you guys do'nt see
anything wrong with this, I will look a bit closer at my fn to display the
numbers on my LCd, but I'm pretty sure that's not the problem since it works
for everything else.

Thanx,

Jai




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