Lpc2000

Now there is a reason not to bring a pin out.

At 09:47 PM 7/8/04 +0000, you wrote:
>I thought that the check sum over the interrupt vectors was
>calculated and written automatically by the device at the end of an
>ISP download. Is there evidence that this technique can fail if the
>ISP download is aborted before it has completed? (valid interrupt
>vector check sum without any code). Perhaps we should experiment a
>little to avoid getting caught out.

I've already experienced it (not deliberately).  An interrupted download 
must be re-programed by pulling P0.14 low, otherwise the LPC attempts to 
run whatever portion of the application is already programmed in the 
chip.  I've only noted this because the Philips download program can't 
communicate with the chip to perform a download unless P0.14 is pulled low 
and the chip is reset.

The checksum is definitely calculated by the download software not the 
LPC.  The ISP support on the LPC simply writes arbitrary blocks at given 
locations, it has no concept of a process with a beginning and an end.  The 
order of writes depends on the download software.  From what I remember of 
reviewing the lpc2isp software it calculates the checksum at the beginning 
(seems straight forward enough) and then simply programs the sectors in 
sequence.

 From the visible behaviour it looks like Philips program does the same but 
I'd have to snoop the serial line to be sure.  You could write a custom 
program that programmed the first sector last.  That would reduce the 
window, especially if the block containing the checksum was the last to be 
written.  I'm not sure even that absolutely eliminates the possibility of 
ending up with a problem but the probability becomes quite small.

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