An RFID tag is capable of storing data, receiving a signal from a reader, determining a response taking into account the tag mode and the data, and transmitting a response to the reader. The data includes a first plurality of bits and a second plurality of bits. The tag mode may be set by a current or a prior command by the reader. Depending on the tag mode, the response may be complete, or the second plurality of bits may be truncated, compressed, or encrypted. In an aspect of the invention, the response includes an implicit indication of whether the response is complete, truncated, encrypted, or compressed. In another aspect of the invention, a command from the reader indicates how many bits should be truncated, compressed, or encrypted.