A method and apparatus for programming nonvolatile (flash) memory in a microcontroller. A nonvolatile memory in the microcontroller is connected via data, address and control signal paths to a processor internal to the microcontroller. These paths are not available to the outside world. In order to program the nonvolatile memory, a tester/programmer provides instructions to a test/control interface and the actual programming of the nonvolatile memory is carried out under control of a supervisory ROM forming a part of the microcontroller storing instructions which are carried out by the processor.