In the statement "return EEDATH*256 + EEDATL;"  what's probably=20
happening is that the variable/register EEDATH is not sized properly to=20
handle being multiplied by 256.  Try creating a temporary unsigned int,=20
copying EEDATH to that, then adding EEDATL to it, and then return it.

Cheers,
-Neil.


On 4/6/2012 8:14 AM, AdiCH wrote:
> Hi
>
> I try to read the flash ROM of my PIC16F916 to calculate a checksum.
> I use the MPLAB and the PICC v9.83 Compiler.
>
> I tried this c function:
>
> unsigned int ReadFlash( unsigned int address ) {
>     EEADRL =3D address%256;
>     EEADRH =3D address/256;
>     EEPGD =3D 1; // program memory
>     RD =3D 1;    // read
>     ;
>     ;
>     return EEDATH*256 + EEDATL;
> }
>
> and everything in assembler:
>
> unsigned char low3;
> unsigned char high3;
>
> unsigned int dataFlash;
>
> void main() {
>
>     #asm
>        BCF        _STATUS, 5
>        BCF        _STATUS, 6
>        MOVF       _low3, W
>        BSF        _STATUS, 6
>        MOVWF      _EEADR
>        BCF        _STATUS, 6
>        MOVF       _high3, W
>        BSF        _STATUS, 6
>        MOVWF      _EEADRH
>        BSF        _STATUS, 5
>        BSF        _EECON1, 7
>        BSF        _EECON1, 0
>        NOP
>        NOP
>        BCF        _STATUS, 5
>        MOVF       _EEDATH, W
>        MOVWF      _dataFlash+1
>        CLRF       _dataFlash
>        MOVF       _EEDATA, W
>        IORWF      _dataFlash, F
>        MOVLW      0
>        IORWF      _dataFlash+1, F
>     #endasm
> }
>
> But both are not working, if I debug it most of the time the register EED=
ATA
> and EEDATH have the right value. But if I copy it to the variable dataFla=
sh
> it is 0.
>
> With the mikroC compiler is a function to read the flash that works. But =
I
> can not use this compiler because the build hex file is much bigger and h=
as
> no space on the PIC.
>
> Any idea what is wrong or how I can read the flash ROM?
>
> thanks
>
> Adrian

--=20
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