GSM Tech

[Steve]

Joe Pfeiffer wrote:
> (just a couple of additional comments to what Steve says)
> Steve writes:
>> The GSM Modem as a black box:
>>
>> >From my understanding of the NEO 1973, the GSM modem is roughly
>> analogous to a computer modem from the past.  (Not the cheap "winmodems"
>> that are so abundant these days.)  It is connected via a serial
>> connection to the portion that runs open software and communicates over
>> the GSM network.  TI has provided a set of "AT" commands to preform a
>> limited subset of the functionality that the modem is capable of.  If
>> you want to use more advanced or unintended functionality, you'll have
>> to figure out how to do that on your own.
> 
> The AT commands are actually part of the GSM standard (I don't know if
> TI has agumented, nor if they've implemented all of them).  My
> understanding is that getting any additional functionality out of it
> starts with prying the cover off the chip and goes downhill from
> there :) 

I'd agree with the statement about the AT commands, but I do think its
probably possible to get unintended functionality out of the GSM modem
without resorting to decapping the chip.  After all that is exactly what
the unlockers are doing.

The unlockers are probably a major reason why TI is so paranoid about
the workings of their chipset since that is where the SIM and provider
locks are usually implemented.  I wish I could give you more information
about the techniques they use, but I don't know what they are.  It would
be interesting to find out, but FIC may not appreciate the discussion on
their mailing list either.

-Steve