We Claim:
[Claim 1] A relay apparatus comprising:
a first reception unit to receive first data from a first communication device that
performs communication by a time-triggered scheme;
5 a second reception unit to receive second data and a token from a second
communication device that performs communication by a token-passing scheme;
a first transmission unit to transmit the second data to the first communication device;
a second transmission unit to transmit the first data to the second 10 communication device while holding the token;
a reference-time management unit to acquire a time from reception of the first
data to next reception of the token by the second reception unit as a reference time,
when the first reception unit receives the first data while the second transmission unit
holds the token; and
15 a communication control unit to cause the first reception unit to receive the first
data repeatedly at a communication cycle equal to or longer than the reference time and shorter than an allowable holding time of the token, causes the first transmission unit to transmit the second data repeatedly at the communication cycle, and every time the token is received by the second reception unit, causes the second transmission unit to 20 hold the token until the second transmission unit transmits the first data to the second communication device within a range of the allowable holding time.
[Claim 2] The relay apparatus according to claim 1,
wherein the reference-time management unit notifies the first communication 25 device of the reference time, and
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the communication control unit is notified from the first communication device of the communication cycle decided by the first communication device, causes the first reception unit to receive the first data repeatedly at the communication cycle notified from the first communication device, and causes the first transmission unit to transmit 5 the second data repeatedly at the communication cycle notified from the first communication device.
[Claim 3] The relay apparatus according to claim 1,
wherein, until the reference time is acquired by the reference-time management 10 unit, the communication control unit
causes the first reception unit to receive the first data transmitted from the first communication device at an arbitrary transmission cycle, and
every time the token is received by the second reception unit, causes the second transmission unit to hold the token until the second transmission unit transmits the first 15 data to the second communication device within a range of a random time within the allowable holding time.
[Claim 4] A relay method by a computer including
a first reception unit to receive first data from a first communication device that 20 performs communication by a time-triggered scheme,
a second reception unit to receive second data and a token from a second communication device that performs communication by a token-passing scheme,
a first transmission unit to transmit the second data to the first communication
device, and
25 a second transmission unit to transmit the first data to the second
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communication device while holding the token, the relay method comprising:
acquiring a time from reception of the first data to next reception of the token
by the second reception unit as a reference time, when the first reception unit receives
the first data while the second transmission unit holds the token; and
5 causing the first reception unit to receive the first data repeatedly at a
communication cycle equal to or longer than the reference time and shorter than an allowable holding time of the token, causing the first transmission unit to transmit the second data repeatedly at the communication cycle, and every time the token is received by the second reception unit, causing the second transmission unit to hold the token 10 until the second transmission unit transmits the first data to the second communication device within a range of the allowable holding time.
[Claim 5] A relay program which causes a computer including
a first reception unit to receive first data from a first communication device that 15 performs communication by a time-triggered scheme,
a second reception unit to receive second data and a token from a second communication device that performs communication by a token-passing scheme,
a first transmission unit to transmit the second data to the first communication
device, and
20 a second transmission unit to transmit the first data to the second
communication device while holding the token, to execute:
a reference-time management process of acquiring a time from reception of the first data to next reception of the token by the second reception unit as a reference time, when the first reception unit receives the first data while the second transmission unit 25 holds the token, and
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a communication control process of causing the first reception unit to receive the first data repeatedly at a communication cycle equal to or longer than the reference time and shorter than an allowable holding time of the token, causing the first transmission unit to transmit the second data repeatedly at the communication cycle, 5 and every time the token is received by the second reception unit, causing the second transmission unit to hold the token until the second transmission unit transmits the first data to the second communication device within a range of the allowable holding time.
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