It seems strange that Philips would make this be a hard fuse option. An SFR bit seems to me that it would have been easier to design on to the chip instead of having to put on a different type of technology just to achieve this fuse.

I suppose one rational at the time was that the chip was meant to be a new design to provide new capabilities and also be a replacement for some older chip that they still needed to provide but didn't want to make anymore. IE an older 12 clock chip may replaced by using this chip, giving it a different part number and then use a parallel programming fixture to pop the fuse at the factory.

If this is the case one begins to wonder if there are other fuses on the part as well that disable some of its capabilities so that this one design could back fit to a seris of former part numbers.

Michael Karas