I do not know where "revision control" crept in, I do include a revision marker, and as far as I know the only connection this has with the checksum is that it affect it just like any other data.

Erik

PS 'pacemaker' is the extreme example, anything that would foul up a function outside the uC circuit must be made safe and this goes WAY beyond a checksum check, a checksum check only verify that the code is not corruptED, not that it is not corrupt.

Erik