Cycle synchronization between interconnected sub-networks
First Claim
1. A method to perform a cycle synchronization between interconnected sub-networks, comprising:
- transmitting a respective cycle time information from a reference node connected to one of the sub-networks to cycle masters of all other sub-networks at recurring time instants the cycle time information transmitted by the reference node is a content of a cycle time register thereof; and
adjusting the cycle time of the cycle masters in accordance with the transmission, the adjustment of the cycle time within a cycle master is performed by adjusting the average difference between a time interval of two transmissions of cycle time information of the reference node which is determined by subtracting two succeeding received contents of the cycle time register of the reference node and a time interval of two samplings of the cycle timer which is determined by subtracting two succeeding sample contents of the cycle time register plus a corrective difference to be zero.
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Abstract
A method to perform a cycle synchronization between interconnected sub-networks, in which a reference node connected to one of the sub-networks transmits a respective cycle time information to cycle masters of all other sub-networks at recurring time instants, and the cycle masters of all other sub-networks adjust their cycle time accordingly. An adjustment of the cycle time within a cycle master is performed by determining a first time interval (t1, t1′) in-between two receptions of cycle time information from the reference node with an own clock, determining a second time interval (t2, t2′) in-between two corresponding transmissions of cycle time information from the reference node on basis of the received cycle time information, comparing the first time interval (t1, t1′) and the second time interval (t2, t2′), and adjusting the own cycle length according to the comparison result.
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Citations
26 Claims
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1. A method to perform a cycle synchronization between interconnected sub-networks, comprising:
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transmitting a respective cycle time information from a reference node connected to one of the sub-networks to cycle masters of all other sub-networks at recurring time instants the cycle time information transmitted by the reference node is a content of a cycle time register thereof; and adjusting the cycle time of the cycle masters in accordance with the transmission, the adjustment of the cycle time within a cycle master is performed by adjusting the average difference between a time interval of two transmissions of cycle time information of the reference node which is determined by subtracting two succeeding received contents of the cycle time register of the reference node and a time interval of two samplings of the cycle timer which is determined by subtracting two succeeding sample contents of the cycle time register plus a corrective difference to be zero. - View Dependent Claims (2, 3)
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4. A network node device configured to synchronize cycles in a sub-network, the network node device comprising:
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a local cycle timer; and a cycle synchronizer that comprises; a clock offset estimation means for determining a timing error of the local cycle timer, the timing error representing a frequency deviation between the local cycle timer and a remote cycle timer; and a cycle adjustment loop configured to receive the timing error and to adjust a cycle length of the local cycle timer to a cycle length of the remote cycle timer by adapting the number of ticks per cycle in the local cycle timer to reduce timing error with respect thereto. - View Dependent Claims (5)
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6. A method for performing cycle synchronization in a network of a plurality of interconnected busses, one of which including a reference node and the others of which each comprises a cycle master, comprising:
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receiving, at one or more of said cycle masters, cycle time information from said reference node; and adjusting a cycle length at said one or more of said cycle masters respectively, by a value selected from the group consisting of +n, and −
n ticks based on said received cycle time information if the received cycle time information deviates from a predetermined value by more than a predetermined amount. - View Dependent Claims (7)
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8. A method for performing cycle synchronization in a network comprising a plurality of interconnected busses one of which includes a reference node device and the others of which each including a cycle master device, comprising:
adjusting a cycle duration that determines a cycle frequency of one of said busses including the reference node device or the cycle master device by a correction value selected from +n, and −
n ticks if a deviation of the cycle duration deviates from a predetermined value by more than a predetermined amount.- View Dependent Claims (9, 10, 11, 12, 13)
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14. A cycle synchronizer for use in a network, comprising:
a plurality of interconnected busses, including; a local cycle timer; and means for adjusting a cycle duration that determines a cycle frequency of said local cycle timer by a correction value selected from +n, and −
n ticks if a deviation of said cycle duration from a reference cycle duration exceeds a predetermined value.- View Dependent Claims (15, 16, 17)
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18. A network comprising:
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a plurality of interconnected busses including a first bus and a second bus remote to said first bus; and a first network device as a local node of said first bus, wherein said first network device includes, a local cycle timer; and cycle duration adjustment means configured for adjusting cycle duration that determines a cycle frequency of said local cycle timer by a correction value selected from +n, and −
n ticks if a deviation of said cycle duration from a reference cycle duration exceeds a predetermined value;said first network device is configured such that said cycle frequency of said cycle timer dictates a cycle frequency of said first bus. - View Dependent Claims (19, 20, 21, 22, 23, 24)
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25. A device for performing cycle synchronization in networks including
plurality of local networks in which at least there are a reference node and cycle masters which are connecting to said local networks respectively, the device comprising: -
a receiving unit configured to receiving a reference cycle time information supplied from said reference node and local cycle time information stored in a register of said cycle master connected to said local network; means for detecting a difference between said reference cycle time information and local cycle time information; and means for adjusting counter value of said register based on the detected difference in order to perform said cycle synchronization so that the counter value selected from ternary values consisting of high, middle and low, wherein said adjustment of a center value is limited to +/−
1 value and the adjustment is only allowed to jump between middle and high or between middle to low.
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26. A method to perform a cycle synchronization between interconnected networks using a reference node as a cycle time master and one or more cycle masters having adjustable own clocks, each of the cycle masters connected to a different one of the interconnected networks, the reference node transmitting a master cycle time information to all other cycle masters at recurring time instants and the cycle masters synchronize the cycle time based on at least the transmitted master cycle time information, the synchronization of the cycle time of the respective cycle master comprising:
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receiving master cycle time information at the recurring time instants; storing the received master cycle time information in a first storage means;
storing cycle time information of the cycle master'"'"'s own clock in a second storage means;determining a first deviation between the received master cycle time information and previously stored master cycle time information; determining a second deviation between the cycle master'"'"'s current cycle time and a previously stored cycle time of the same cycle master; and comparing the determined first deviation and second deviation and adjusting the cycle master'"'"'s cycle time.
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Specification