A fastening power tool such as a nailer is provided including a tool housing, an input unit actuated in response to an operator input, and a motor assembly including a motor housed within the tool housing. A control unit is provided including a controller programmable to control an operation of the motor and a decoder circuit configured to control a supply of power from a power source to the controller based on a status of the power source and a status of the input unit. The decoder circuit is configured to connect supply of power from the power source to the controller when the power tool is coupled to the power source prior to an engagement of the input unit, but disconnect the supply of power when the power tool is coupled to the power source after the engagement of the input unit.