Lpc2000

Rather than using external gates to trigger the scope, it may be just
as easy to use a spare IO pin and set it when the Start condition is
set by I2C0CONSET=0x20 (or similar).  Then clear the pin upon entry
into the interrupt routine.

I posted a reply similar to this earlier.  It appears to have gotten
lost.  If it shows up, I will delete it.

Richard