I am adding an A/D capability to an existing controller design. This involves migrating from a 16C54 to a 16C710. There seems to be a big difference in the robustness of the oscillator. In both cases, I'm using a 2 MHz Matsushita resonator with built-in caps and the config choice set to XT. The 16C54 is pretty bulletproof. You can hook a scope probe or a logic probe to OSC1 or OSC2 and it keeps right on going. The 16C710 quits at the slightest loading. That makes me worry about possible stability problems and frequent unwanted resets. Just to see what would happen, I programmed a 16C710 to use the config choice HS. Big improvement. Now it acts like the 16C54. But HS is not normally the config setting for a 2 MHz part. Anyone have any comments/suggestions/guidance? Reg Neale