Re: [Flashforth-devel] FlashForth V3.6 PIC18F4550 / small ? - big question

[Mikael N. <mik...@pp...>]

On 8.2.2011 17:03, R. M. Hessler wrote:
> Hello Mikael,
>
> after a lot of struggle, the problems still alive. So I refer to
> your text “Problems” -->
>
> Please note that the chips 18F252, 18F452, 18F258, 18F458,
> do not work reliably if you jump over the $3fff address border.
> So these chips are NOT recommended for FlashForth if your
> program grows over the $3fff border.
> This is a fault in the PIC chip, not in FlashForth. The other
> 18Fxxxx chips do not have any such errata.
>
> May be that my problems begin at $3fff too. Errata didn't
> show some reference to related topics, or I didn't notice.
>
> The question is, how to find out certainly the behaviour of
> the chip in this case and what's about workarounds. Because
> there are sources, producing working code ending at about
> $ 6990, it should give hope for me, isn't it so?
>
> On the other side, which chip is proven save in operating?
>
> Best wishes from Prüm/Eifel out of the first spring messengers
> with blue sky and 14 Grad Celsius
> Gruss / Robert
>

When compiling, there are no jumps over the 3fff border.
But there could be some other problems related to that border I do not 
know of.
My programs are usually pretty small, I have never filled a complete 
chip yet.

I have been using 252 258 and 2520 and 2455 mostly.

Some questions for you.
Have you tried many different chips or just one ?
Have you tried other UART speeds 4800 9600 19200 38400 ?
Have you tried to blank the chip and reflash FF ?
What is your clock speed ?
Have you tried lower/higher clock speeds ?

Gruess Mike