Question

I want to use Claudiu Chiculitas tiny bootloader for PIC16 (i have modyfied it to suit my chip) but since that bootloader does not move code to prevent overwriting the bootloader, I must somehow manually see to that the bootloader is not overwritten. I have tried to use the –rom option like this:

--rom=default,-0-4,-3f00-3fff

What I want is: No code in the first 4 words of code memmory, because thats where the jump to the bootloader is and no code in the last 128 words of memory because thats where the actual bootloader is. –rom like I use it does nothing. Im using HI-TECH PICC STD COMPILER (Microchip PICmicro) V9.60PL3 and the chip is pic16f876A.

Answer 1

You can also do this with a custom linker script. Usually, your linker script would contain these lines to put the reset vectors first and the code (in the page named “page”) behind it:

CODEPAGE   NAME=vectors    START=0x0            END=0x29           PROTECTED
CODEPAGE   NAME=page       START=0x2A           END=0x7FFF

For the bootloader used in Microchip’s FSDem board (which occupies the 0x0-0x800 range, and expects your program to have its own vectors at 0x800), this is replaced by the lines below which prevent the linker from using anything below 0x800:

CODEPAGE   NAME=boot       START=0x0            END=0x7FF          PROTECTED
CODEPAGE   NAME=vectors    START=0x800          END=0x0x829        PROTECTED
CODEPAGE   NAME=page       START=0x82A          END=0x7FFF