COMMUNICATION UNIT, COMMUNICATION METHOD AND RECORDING MEDIUM

PROBLEM TO BE SOLVED: To select a proper resonance frequency from a transmission reception state and to switch to it. SOLUTION: In a step S1, a controller transmits a Read Command to a receiver side communication unit to request the communication unit to transmit data stored in a prescribed block of a memory. Upon the receipt of the Read Command, the receiver side communication unit returns a Read Response, and when not receiving the Read Command, the communication unit returns no Read Response. In a step S2, the controller discriminates whether the controller has received the Read Response. When the controller discriminates that the controller has received the Read Response, the controller discriminates that the controller is in a communication enable state with the receiver side communication unit in a step S3, and executes information communication. When the controller discriminates that the controller has received no Read Response, the controller changes a resonance frequency of an antenna in a step S4. The processing returns to the step S1 and the processing after the step S1 is repeated.