[time-nuts] FE-5680A firmware dump

Azelio Boriani azelio.boriani at screen.it
Fri Feb 17 17:38:24 UTC 2012


Maybe. Take into account that MCS51 OTP processors usually are 8K of code.
I use, among the others, the AT89C55 that has 20K of flash ROM. It seems
better to use a ROMless 8051 and place the code/tables in the PSD.

On Fri, Feb 17, 2012 at 6:17 PM, Bob Camp <lists at rtty.us> wrote:

> Hi
>
> I'd bet that there's some code in there and some data tables. Without
> digging in, it's hard to say how big each is. We could easily find that
> there's 24K of code in the MCS51 and a bunch of tables in the PSD813.
>
> Bob
>
> -----Original Message-----
> From: time-nuts-bounces at febo.com [mailto:time-nuts-bounces at febo.com] On
> Behalf Of Azelio Boriani
> Sent: Friday, February 17, 2012 6:06 AM
> To: Discussion of precise time and frequency measurement
> Subject: Re: [time-nuts] FE-5680A firmware dump
>
> OK, then maybe there are ROM bank switching as the MCS51 can't execute
> beyon the 64K limit. It can be very challenging to follow a code that jumps
> between 64K ROM banks. Moreover the MCS51 has to address the external RAM
> by massive pointer use (the famous MOVX @DPTR,A and MOVX A, at DPTR
> instructions) beyond the 256byte internal easier to address RAM. Yes, you
> need a good disassembler, aware of bank switching and massive pointer use.
>
> On Fri, Feb 17, 2012 at 11:20 AM, Javier Herrero
> <jherrero at hvsistemas.es>wrote:
>
> > Don forget the PSD813 :) It provides 128KB Flash and 8KB RAM... so it can
> > be a bit more complicated
> >
> > Regards,
> >
> > Javier
> >
> > El 17/02/2012 11:09, Azelio Boriani escribió:
> >
> >> In my opinion you don't need the power of an IDA-class disassembler to
> >> process an 8051-like code. The MCS51 family processors have only 128 or
> >> 256
> >> bytes of RAM (and at most 64K ROM) and cannot host complex code.
> >>
> >> On Fri, Feb 17, 2012 at 10:27 AM, Elio Corbolante<eliocor at gmail.com>
> >>  wrote:
> >>
> >>  From: Mike McCauley
> >>>
> >>>> I've been considering ripping the firmware from the mcu as well.  I've
> >>>>>>
> >>>>> not
> >>>
> >>>> got beyond the consideration stages, but i have all the equipment here
> >>>>>>
> >>>>> at
> >>>
> >>>> work. When you say that the read option is not available. is this
> >>>>>>
> >>>>> because
> >>>
> >>>> the chip has protection fuses enabled?
> >>>>>>
> >>>>> Id like to help with the disassembly if you can get the binary dump.
> >>>>
> >>>
> >>> Don't worry: when I will be able to dump the firmware I will let it on
> >>> the
> >>> public domain.
> >>> BTW, I have the opportunity to use the IDA disassembler (a friend of
> mine
> >>> is a licensed user) so I think the disassembly of the code will be
> rather
> >>> good.
> >>> Any knowledge of a public domain 8051 disassembler which can rival IDA
> in
> >>> performance/code analysis?
> >>>
> >>> _     Elio.
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