A microprocessor architecture which permits automatic programming of a non-volatile memory included on the same chip as a processing and control unit. The microprocessor includes a permanent memory such as an EPROM which can be electrically written word by word. The microprocessor additionally includes a processing and control unit connected to the permanent memory through two sets of data and address registers. Circuits are also included for distributing memory write voltage in a manner which does not interfere with normal operation of the microprocessor. As a result, the data contents at one memory location can be modified (written) the same time instructions are being read from another memory location. Memory writing can alternatively be effected by a sub-program comprising a sequence of microinstructions, or by a write automaton comprising hard-wired logic circuits.