Lpc2000

At 10:19 PM 2/1/05 +0000, you wrote:
>Build the loader into the existing code.  This will, when prompted by
>the host, prepare and erase upper sectors, accept a chunk (512B or
>8KB?) of the new code from the host, and store it in RAM.
>
>Each chunk of new code will be programmed to the blank sectors after a
>CRC check.
>
>When done, a global CRC will be performed.
>
>Questions:
>
>How to transfer execution to the new code segment?


Jump table?  If you place a vector table of functions at a fixed place in 
the download area it can be replaced repeatedly.  I suspect you will need a 
fixed boot block in any case so this would fit quite well.

>What about the vector table?


There's not a great deal to be concerned about there I think.  The IRQ is 
vectored through the VIC so it's code won't change.  That leaves the 
startup vector which should always go to the boot block so it's fixed. The 
FIQ might be an issue if you really need a high performance FIQ.  I suppose 
you could jump to a fixed location if you needed to.  The other exceptions 
can either be dealt with in the boot block or though the above mentioned 
jump table,  Most of them will probably be fatal in any case.

>Other ignorance on my part?


Some way to verify that the active (non-boot block) program is valid.

Robert

" 'Freedom' has no meaning of itself.  There are always restrictions,
be they legal, genetic, or physical.  If you don't believe me, try to
chew a radio signal. "

                         Kelvin Throop, III