Transponder interface circuit

Abstract

A transponder interface circuit (172) operates to allow communication between a transponder controller (104) and external circuitry. The interface circuit (172) has a buffer memory (184,186) that allows the transponder controller (104) and the external circuitry each to transmit data at either the transponder's (14) or the external circuitry's clock rate without complicated protocols for direct communication. Each of the transponder controller (104) and the external circuit may be enabled by an interface controller (174) to assume control of the buffer memory (184,186). By using the buffer memory (184,186) and interface controller (174), whichever of the transponder controller (104) and the external circuitry is transmitting or receiving data may fill or empty the buffer memory (184,186) at either the transponder controller's (104) or the external circuitry's chosen clock rate. The interface controller (174) will monitor the transfer such that when the buffer memory (184,186) is full or empty, the interface controller (174) will send a command to the appropriate transponder controller (104) or external circuit to either receive data from the full buffer memory (184,186) or transmit data to the empty buffer memory (184,186).