Fredrik Axtelius wrote:

> Hi!
>
> Short version:
> I really have no clue how the bootloader writes to program memory but...
> Does LVP need to be enabled for a bootloader to work?
>
> Long version:
> Im using a bootloader from www.microchipc.com for uploading my code to
> a 16F877. So far everything has worked just great but now im working on
> a project where I need to use the RB3/PGM.
>
> In earlier projects I have tied this to GND sice I don't do LVP
> programming. So now I pulled it down instead, configured the pin
> as output but it doesn't work.
>
> I read through the datasheet and found this:
> "Low Voltage ICSP Programming (LVP) is enabled by default, which
> disables the RB3 I/O function. LVP must be disabled to enable RB3
> as an I/O pin and allow maximum compatibility to the other 28-pin and
> 40-pin mid-range devices."
>
> Makes sense but since im using a bootloader the fuses are set there.
> No problem, changed the source so LVP is off, recompiled and burned it
> and now the bootloader wont't work. No response what so ever.
>
> I verified the new version with the old and the only thing that differs
> is the configbit for LVP which now is off.
>
> tia
> /Fredrik

BEWARE: within the config word there are write protect bits that explicitly
enable/disable the ability of an executing program to write to program memory.
If these bits are programmed incorrectly your bootloader CANNOT work. Also watch
out for A and non-A parts, some of the config bits have different meanings
(effects).

Regards
Sergio Masci

http://www.xcprod.com/titan/XCSB - optimising structured PIC BASIC compiler

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