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1. US20090172198 - System and method for synchronising a data processing network

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Claims

1. A data processing system comprising a group of at least a first and a second module, wherein each module has a data processing facility, a mutually independent clock for timing data transmissions from a module to another module, and a time-slot counter for counting a number of time slots which are available for transmission of data, the modules having a first operational state wherein the counted number of time slots is less than or equal to a predetermined number, in which operational state data transmission is enabled, and a second operational state wherein the number is in excess of the predetermined number, in which second operational state data transmission is disabled, each module having a notifying facility for notifying when said module is in the second operational state, the data processing system having a detecting facility for detecting whether all other modules have notified that said all other modules are in the second operational state, the modules having an initialization facility for resetting the time-slot counter when the module is in the second operational state and each of the other modules has notified that said each of the other modules is in the second operational state.
2. The system according to claim 1, wherein a cycle time of the clocks of the modules differs by at most a predetermined fraction of an average cycle time, and the duration of the predetermined number of time slots is less than a reciprocal value of said fraction.
3. The system according to claim 2, wherein the duration of the predetermined number of time slots is greater than one quarter of the reciprocal value and is less than three quarters of the reciprocal value.
4. The system according to claim 1, having a further group of modules as specified in claim 1, wherein modules from a first subset of the first, second and third modules notify modules from a first subset of the further group when they are in the second operational state, and wherein modules from a second subset of the further group notify modules from a second subset of the first, second and third modules when they are in the second operational state.
5. Method for operating a data-processing system, comprising a group of at least a first and a second module having mutually independent clocks, which method comprises for each module the steps of
a. initializing a counter for counting a number of time slots,
b. at each time slot determining whether data is available for transmission to another module, and if that is the case transmitting said data,
c. at each time slot incrementing the count for the number of time slots,
d. repeating the method from step b if the counted number is not in excess of a predetermined number,
e. if the counted number is in excess of the predetermined number notifying this to the other modules of the group,
f. waiting until the other modules of the group have notified that the predetermined number is excessed, and
g. repeating the method from step a.
6. A data processing system comprising:
first, second, and third modules, each module comprising:
a data processing facility;
a mutually independent clock for timing data transmissions from a module to another module; and
first and second time-slot counters for counting a number of time slots which are available for transmission of data, wherein the modules have a first operational state wherein the counted number of time slots is less than or equal to a predetermined number in which operational state data transmission is enabled, and a second operational state wherein the number is in excess of the predetermined number in which second operational state data transmission is disabled,
wherein the second module further comprises:
a first notifying facility for notifying the first module when the second module is in the second operational state and a second notifying facility for notifying the third module when the second module is in the second operational state, the first notifying facility operating independently of the second notifying facility;
a first detecting facility for detecting whether the first module has notified that it is in the second operational state, and a second detecting facility for detecting whether the third module has notified that it is in the second operational state; and
a first initialization facility for resetting the first time-slot counter when the first and second modules are in the second operational state, and a second initialization facility for resetting the second time-slot counter when the second and third modules are in the second operational state, the first initialization facility operating independently of the second initialization facility.