CODEWITHSUNDEEP
c++pic18flash-memory
user3932504
user3932504

Reputation: 1

Unable to write to flash program memory(PIC18F4620)

im trying to write some data into the flash program memory. i read the data sheet and followed the step. And also i edited the linker script for the rom array. below are my codes for flash program memory sequences in C. im trying to write into address 0xFF00. 

            TBLPTR = 0x3fc000;           // start of erase seq
            EECON1 = 0b10010100;         //EEPGD = 1, FREE = 1, WREN = 1,
            INTCONbits.GIE = 0;
            EECON2 = 0x55;
            EECON2 = 0xAA;
            EECON1bits.WR = 1;           
            INTCONbits.GIE = 1;
            EECON1bits.WREN = 0;    

            TBLPTRU = 0x3F;              // start of write seq
            TBLPTRH = 0xC0;
            TBLPTRL = 0x00;
            for(i = 0; i<64; i++)
            {

                TABLAT = dispData0[i];
                TBLPTRL = i;
            }   
            EECON1 = 0b10000100;         // EEPGD = 1, WREN = 1
            INTCONbits.GIE = 0;
            EECON2 = 0x55;
            EECON2 = 0xAA;
            EECON1bits.WR = 1;
            INTCONbits.GIE = 1;
            EECON1bits.WREN = 0;

            TBLPTR = 0x00ff00;
            dispData3[0] = TABLAT;
            TBLPTR++;
            dispData3[1] = TABLAT;

below are the linker script i have edited :

    // File: 18f4620_e.lkr
// Sample linker script for the PIC18F4620 processor

LIBPATH .

FILES c018i_e.o
FILES clib_e.lib
FILES p18f4620_e.lib

CODEPAGE   NAME=page       START=0x0               END=0xFEFF
CODEPAGE   NAME=para       START=0xFF00            END=0xFFFF         PROTECTED
CODEPAGE   NAME=idlocs     START=0x200000          END=0x200007       PROTECTED
CODEPAGE   NAME=config     START=0x300000          END=0x30000D       PROTECTED
CODEPAGE   NAME=devid      START=0x3FFFFE          END=0x3FFFFF       PROTECTED
CODEPAGE   NAME=eedata     START=0xF00000          END=0xF003FF       PROTECTED

DATABANK   NAME=gpre       START=0x0            END=0x5F
ACCESSBANK NAME=accessram  START=0x60           END=0x7F
DATABANK   NAME=gpr0       START=0x80           END=0xFF
DATABANK   NAME=gpr1       START=0x100          END=0x1FF
DATABANK   NAME=gpr2       START=0x200          END=0x2FF
DATABANK   NAME=gpr3       START=0x300          END=0x3FF
DATABANK   NAME=gpr4       START=0x400          END=0x4FF
DATABANK   NAME=gpr5       START=0x500          END=0x5FF
DATABANK   NAME=gpr6       START=0x600          END=0x6FF
DATABANK   NAME=gpr7       START=0x700          END=0x7FF
DATABANK   NAME=gpr8       START=0x800          END=0x8FF
DATABANK   NAME=gpr9       START=0x900          END=0x9FF
DATABANK   NAME=gpr10      START=0xA00          END=0xAFF
DATABANK   NAME=gpr11      START=0xB00          END=0xBFF
DATABANK   NAME=gpr12      START=0xC00          END=0xCFF
DATABANK   NAME=gpr13      START=0xD00          END=0xDFF
DATABANK   NAME=gpr14      START=0xE00          END=0xEFF
DATABANK   NAME=gpr15      START=0xF00          END=0xF7F
ACCESSBANK NAME=accesssfr  START=0xF80          END=0xFFF          PROTECTED

SECTION    NAME=CONFIG     ROM=config
SECTION    NAME=DATTBL     ROM=para

STACK SIZE=0x100 RAM=gpr14

Upvotes: 0

Views: 910

Answers (1)

Ross Ridge
Ross Ridge

Reputation: 39601

There's two problems with your code. The first is that you're trying to erase and write the flash memory at address 0x3FC000 while trying to read from it at address 0x00FF00. The second is that read and writing from TBLLAT doesn't actually perform the read or write operation. It's just a staging register, to perform the read or write you need to use the TBLRD or TBLWT instruction. These instruction aren't available in C, so you need to use inline assembly:

 TBLPTR = 0x00FF000      // start of write seq
 for(i = 0; i<64; i++) {
     TABLAT = dispData0[i];
     _asm TBLWTPOSTINC _endasm // write TBLLAT to flash; increment TBLPTR
 }

 ...

 TBLPTR = 0x00FF00;
 _asm TBLRDPOSTINC _endasm //  read flash into TBLLAT; increment TBLPTR
 dispData3[0] = TABLAT;
 _asm TBLRDPOSTINC _endasm
 dispData3[1] = TABLAT;

I found about the TBLWTPOSTINC inline assembly instruction from this post on the Microchip forums: http://www.microchip.com/forums/m653617.aspx#msg653672

Upvotes: 2

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