The TK5552 is a complete programmable R/W transponder that implements all important functions for identification systems. It allows the contactless reading (uplink) and writing (downlink) of data which are transmitted bi-directionally between a read/write base station and the transponder. It is a plastic cube device which accomodates the IDIC transponder IC and the antenna is realized as an LC circuit. No additional external power supply is necessary for the transponder because it receives power from the RF field generated by the base station. Data is transmitted by modulating the amplitude of the RF field (uplink mode). The TK5552 can be used to adjust and modify the ID code or any other stored data, e.g., rolling code systems. The on-chip 1056-bit EEPROM (32 blocks, 33 bits per block) can be read (uplink) and written (downlink) blockwise from the base station. The blocks can be protected against overwriting. One block is reserved for setting the operation modes of the IC.