A microcontroller having a memory programmable in user mode. The microcontroller contains circuitry for detecting whether a programming level voltage has been activated. Also included is a Longwrite enable register containing an enable bit for enabling/disabling programming of the memory. When the register contains the bit indicating programming as enabled, and the programming level voltage is detected, the microcontroller allows the program memory to be programmed. The programming can take place in user mode. The programming level voltage signal is also used to detect whether to enter into a test mode. Programming of the program memory is also possible in the test mode. The invention is also directed to a method for operating a microcontroller for controlling programming of the program memory. The microcontroller according to the invention allows increased functionality by detecting whether to enter the test mode without the requirement of a test mode select input signal.