Abstract: A microcontroller fabricated on a semiconductor chip has an on-chip EPROM program memory. The microcontroller is selectively configurable to operate in any one of a plurality of predetermined operating modes, including at least one secure microcontroller mode. A plurality of EPROM configuration fuses used for configuring the microcontroller and protecting its program memory from read, verify or write through any instruction initiated from other than a predetermined secure area of the chip, are mapped into the on-chip EPROM program memory as bits in respective address locations thereof. The value of a bit representing any one of said fuses is effective to determine the condition of the respective fuse. That condition is observed by reading the value of the respective bit for that fuse stored in the EPROM program memory.

Abstract: A semiconductor microcontroller includes the capability to perform analog to digital conversions of an analog signal representative of a variable parameter indicative of the need to exercise a control function. While the analog to digital conversions are being performed, the microcontroller processor can be powered down to eliminate noise arising from switching activities of the processor as a source of inaccuracy in the conversion process. At the end of the conversion, the analog to digital converter can either shut itself down or wake up the processor. The powering down is achieved by simply disabling the clock input to the microcontroller so that the processor is still activated but incapable of undergoing switching functions.