Subject: Re: PIC16F877A
Date: Mon, 14 Oct 2002 15:27:52 -0400
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"Marco Tuzzi" wrote in message
> I once had a problem with a uC which showed strange behavior.
> The problem was that when the uC wrote into flash, reading from it before
> the actual writing finished didn't output the "real" data, but a control
> flag representing the status of the writing process.
> Since the code of you program is in flash, when the PIC is writing in
> it can't goo on with normal opperations, since it can't read instructions;
> it reads from flash the control flag during write but it "thinks" it's an
> instruction from your code; so it executes nonsense!
> May it be the problem?
I don't beleive so...
> To avoid this, I had to copy part of the code to RAM and swith to
> the code from RAM when the uC was writing into flash. then, after the
> command finished, I switched back to executing from Flash.
there is no way to do that with a pic chip. code has to execute in the code
> "dhrm77" ha scritto nel messaggio
> > I was actually one of the first one to receive a version of picstart's
> > firmware from Microchip only a few days ago, that was able to program
> > PIC16F877A. Until now, MPLAB was able to handle the 877A, but not
> > I upgraded picstart to the latest version 3.00.40. and was finally able
> > program those new chips. We verified the chips to make sure that they
> > programmed correctly. The 877 and the 877A have the exact same hex
> > One works, not the other....
> > About the erratic behavior..
> > It seems that depending on WHERE the code is located in memory, the code
> > exhibit different malfunctions.
> > This seems to point to a problem accessing the right location of the
> > some cases by the core, or problems in jump instructions.... but we
> > haven't been able to pin-point the problem...
> > D.
> > --
> > -
> > "Wouter van Ooijen (www.voti.nl)" wrote in message
> > news:firstname.lastname@example.org...
> > > > > We migrated code from the PIC16F877 to PIC16F877A, and the code
> > doesn't
> > >
> > > >I had the same problem with the 509 and 509A it was tracked down to
> > > >programmer
> > >
> > > So make sure your programmer can handle an 877A, the programming
> > > algorithms for 877 and 877A are quite different (I know, I implemented
> > > both in my programmer).
> > >
> > >
> > > Wouter van Ooijen
> > >
> > > -- ------------------------------------
> > > http://www.voti.nl
> > > PICmicro chips, programmers, consulting