Fuzzy logic extends a general purpose instruction set

By extending the general purpose instruction set of the CPU12 to include four new fuzzy logic instructions, the 16-bit MC68HC12 gains more than an order of magnitude improvement in execution speed for a fuzzy inference program compared to the 8-bit MCS8HC11. Coding is also dramatically simplified by reducing a 250 byte program to about 50 bytes. At the same time, re-use of existing logic in the CPU allows these additions without increasing the die size (and thus cost) of the MCU. The general purpose instruction set provides the means for programming non-fuzzy portions of the embedded control application as well as large portions of the inference program itself. This makes it possible for the fuzzy instructions to be focused on the portions of the fuzzy algorithm where they can produce the most benefits. Any of the specialized fuzzy instructions can be replaced by an alternate algorithm coded with traditional general purpose instructions. This provides a great deal of flexibility not found in hardware approaches.