This paper describes the Passive Active RFID Tag (PART). The first innovation is an automated method to generate RFID tag controllers based on high-level descriptions of a customised set of RFID primitives. We are capable of targeting microprocessor-based or custom hardware-based controllers. The second innovation is a passive burst switch front-end to the active tag. This switch reduces power consumption by allowing the active transceiver and controller to sleep when no reader is querying the tag. When RF energy is supplied by the reader, the burst switch 'wakes-up' the tag to process the primitive. A prototype burst switch is demonstrated using a Real-Time Spectrum Analyser (RTSA) from our RFID Center for Excellence. We demonstrate the customised RFID tag controller with 40 primitives using a Xilinx Coolrunner-II requiring 1.29 mW and 50 µW of power when active and asleep, respectively. We also present a PIC-microcontroller and hardwarebased Nano Tag at 2.7µW.