Process of operating a processor with domains and clocks

A data processing device formed in a single semiconductor chip. The data processing device includes an electronic processor, and on-chip peripheral circuitry ordinarily operative together. Further included, are means for selectively entering externally supplied data into the electronic processor and on-chip peripheral circuitry, for starting and stopping operations of the electronic processor and the on-chip peripheral circuitry independently of each other in an emulation mode of operation.