Abstract: A communication system (500) has a plurality of communication apparatuses (100). A management verification unit (110) verifies whether or not a communication apparatus (100) is a network management master. A grandmaster verification unit (120) verifies whether or not the communication apparatus (100) is a grandmaster. When the communication apparatus (100) is the network management master and the grandmaster, a setting unit (130) sets in an apparatus priority (21) a threshold (23) indicating that a priority is higher than a priority of a current grandmaster. When the communication apparatus (100) is the network management master and not the grandmaster, the setting unit (130) transmits a network setting message that includes the threshold (23) to be set for a priority of another communication apparatus that is the grandmaster.

Abstract: A communication system (500) includes a plurality of communication apparatuses (100) and selects from the plurality of communication apparatuses (100), a grandmaster that is to be a standard of time. A difference calculation unit (110), when receiving a synchronization message that includes time of the grandmaster from the grandmaster, calculates a time difference between the time of the grandmaster and time of the communication apparatus (100). A correction unit (120) changes count speed of a time counter that counts the time of the communication apparatus (100) in a way that the time of the communication apparatus (100) synchronizes with the time of the grandmaster at a time when a time correction period that is specified beforehand elapses, based on the time difference.

Abstract: A frequency deviation change rate computation unit (204) computes a frequency deviation change rate being a change rate per unit time of a frequency deviation between a clock frequency of a synchronization reference device serving as a reference of time synchronization and a clock frequency of a time synchronization device which performs time synchronization with the synchronization reference device.

Abstract: A priority verification unit (110) obtains from, among a plurality of communication apparatuses, other communication apparatus other than a current grandmaster, a grandmaster mediation message that is a grandmaster mediation message used for selecting a grandmaster and that includes a priority of the other communication apparatus. The priority verification unit (110) verifies whether or not the priority of the other communication apparatus is higher than a grandmaster priority (22). A mediation unit (120), when the priority of the other communication apparatus is verified as being higher than the grandmaster priority (22), to obtain a synchronization message including time of the other communication apparatus from the other communication apparatus before switching the other communication apparatus to the grandmaster.

Abstract: A grand master device (GM) (10) and a slave device (S1) (20) are connected via a general-purpose hub (HUB) (30) whose relay delay is not constant. The grand master device (GM) (10), at a timing for transmitting a Sync frame for time synchronization, acquires current time as transmission time of the Sync frame, acquires a count value of a master counter as a transmission count value, stores the transmission time and the transmission count value in the Sync frame, and transmits the Sync frame. The slave device (S1) (20) receives the Sync frame, acquires reception time of the Sync frame and a reception count value which is a count value of a slave counter at the reception time, and corrects time of the slave device (S1) (20), using the transmission time, the transmission count value, the reception time and the reception count value.

Abstract: A priority verification unit (110) obtains from, among a plurality of communication apparatuses, other communication apparatus other than a current grandmaster, a grandmaster mediation message that is a grandmaster mediation message used for selecting a grandmaster and that includes a priority of the other communication apparatus. The priority verification unit (110) verifies whether or not the priority of the other communication apparatus is higher than a grandmaster priority (22). A mediation unit (120), when the priority of the other communication apparatus is verified as being higher than the grandmaster priority (22), to obtain a synchronization message including time of the other communication apparatus from the other communication apparatus before switching the other communication apparatus to the grandmaster.

Abstract: A communication system (500) has a plurality of communication apparatuses (100). A management verification unit (110) verifies whether or not a communication apparatus (100) is a network management master. A grandmaster verification unit (120) verifies whether or not the communication apparatus (100) is a grandmaster. When the communication apparatus (100) is the network management master and the grandmaster, a setting unit (130) sets in an apparatus priority (21) a threshold (23) indicating that a priority is higher than a priority of a current grandmaster. When the communication apparatus (100) is the network management master and not the grandmaster, the setting unit (130) transmits a network setting message that includes the threshold (23) to be set for a priority of another communication apparatus that is the grandmaster.

Abstract: A communication system (500) includes a plurality of communication apparatuses (100) and selects from the plurality of communication apparatuses (100), a grandmaster that is to be a standard of time. A difference calculation unit (110), when receiving a synchronization message that includes time of the grandmaster from the grandmaster, calculates a time difference between the time of the grandmaster and time of the communication apparatus (100). A correction unit (120) changes count speed of a time counter that counts the time of the communication apparatus (100) in a way that the time of the communication apparatus (100) synchronizes with the time of the grandmaster at a time when a time correction period that is specified beforehand elapses, based on the time difference.

Abstract: A token management slave device is included in a communication system. The communication system includes a master device, time asynchronous slave devices communicating with the master device and not being time synchronized with the master device, and time synchronous slave devices communicating with the master device and being time synchronized with the master device. The token management slave device sets an asynchronous communication period in which the master device and the time asynchronous slave devices communicate, between a plurality of synchronous communication periods that is a plurality of periods in which the master device and the time synchronous slave devices communicate. Then, the token management slave device instructs the time asynchronous slave devices to communicate with the master device, when the asynchronous communication period arrives.