Which is why I asked about the reason for using the F124 rather than the F020, which is virtually identical but is 'only' half as fast (25MHz max. compared to 50MHz).


But surely the edge speed only affects radiated EMI? What matters for immunity are the propagation delays of the internal circuits. The shorter these are, the more vulnerable the device will be.
Of course propagation delay (tpd) and edge speed (tr) are not completely unrelated; a circuit with shorter tpd is bound to have a shorter tr too, but the physical effect of the two is different.



But you haven't told us about the decoupling scheme used for the processor. As I said earlier, this is a very important issue.


Rob.