| 摘要 |
A transmission device can continue secure communication having a consistency between a frame counter of a transmission device and a frame counter of a reception device without bothering a user, even if the frame counter is reset due to battery exchange, power cut off, or the like. The transmission device includes: a transmission frame counter (20) that counts a value monotonically incremented for each packet transmission and holds the value as a frame counter value; a transmission unit that adds the frame counter value held in the transmission frame counter (20) to a packet, and transmits the packet to the reception device (200); and a transmission frame counter storage circuit (23) that stores the frame counter value. The transmission frame counter (20) (i) stores the counted and held frame counter value into the transmission frame counter storage circuit (23) for each stored-frame-counter updating increment that is a natural number greater than an increment by which the frame counter value is monotonically incremented, and (ii) holds, as a new frame counter value, the frame counter value stored in the transmission frame counter storage circuit (23) added with the stored-frame-counter updating increment, when the transmission device (100) is reset.
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