Token device for distributed time scheduling in a data processing system
First Claim
Patent Images
1. A data processing system comprising:
- a communication bus; and
a multiplicity of data handling devices connected to the bus, each device communicating to the other devices through the bus by means of an encoded bus token signal passed on the communication bus from one device to another in an established logical order, the device currently in possession of the bus token signal being allowed to transmit over the bus, for each of certain devices of the data handling devices the bus token signal providing an indication of a time at which each certain device is to temporarily gain possession of the bus token signal out of the established order and perform a respective time critical operation, each indication of time on the bus token signal referencing the time of the respective time critical operation.
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Abstract
A token passing media access protocol provides distributed time scheduling. The token provides an indication of each time at which a network device is to perform a cyclic or time critical operation. The token also provides an indication of system time to enable all devices on the network bus to be synchronized. The format of data transmissions on the network bus employs a shortened device address when referencing the device as a source. The source address corresponds to a unique portion of the device address.
54 Citations
17 Claims
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1. A data processing system comprising:
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a communication bus; and a multiplicity of data handling devices connected to the bus, each device communicating to the other devices through the bus by means of an encoded bus token signal passed on the communication bus from one device to another in an established logical order, the device currently in possession of the bus token signal being allowed to transmit over the bus, for each of certain devices of the data handling devices the bus token signal providing an indication of a time at which each certain device is to temporarily gain possession of the bus token signal out of the established order and perform a respective time critical operation, each indication of time on the bus token signal referencing the time of the respective time critical operation. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
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9. A local area network comprising:
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a communication bus; and a plurality of devices connected to the bus, each device communicating to the other devices through the bus by means of an encoded bus token signal passable on the bus from one device to another in an established logical order to enable one device at a time to transmit over the bus, the bus token signal comprising; an indicator element for indicating a last transmitted time synchronization message, each device upon receiving the bus token signal checking for an indication of receipt of the message; and a reservation element for indicating times at which the bus token signal is to be passed from the device in possession of the bus token signal to a certain device not necessarily the next device in the established order such that the certain device is able to perform a time dependent operation. - View Dependent Claims (10, 11)
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12. A data processing system comprising:
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a communication bus; a multiplicity of devices including a master device connected to the bus, each device communicating to other devices through the bus, the master device periodically providing time synchronization messages to the other devices at substantially a same time to synchronize the devices connected to the bus; and an encoded bus token signal for indicating the last time synchronization message provided by the master device to the other devices, the bus token signal being passed on the communication bus from one device to another to enable each device to check the last time synchronization message as indicated by the bus token signal.
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13. In a data processing system having a multiplicity of devices connected to a communication bus, each device communicating to other devices through the bus, a method for distributing bus communication time comprising the steps of:
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a) providing an encoded bus token signal for passing on the communication bus from one device to another in an established logical order, said bus token signal; allowing bus transmission time to a device currently in possession of the bus token signal, and indicating a time at which each of certain devices connected to the bus is to temporarily gain possession of the bus token signal out of the established order to subsequently perform a time critical operation; b) passing the bus token signal on the bus from one device to another in the established logical order, the device currently in possession of the bus token signal being allowed to transmit over the bus; and c) at a time indicated on the bus token signal, interrupting the device currently in possession and passing the bus token signal to the certain device which is to gain possession of the bus token signal out of the established order. - View Dependent Claims (14, 15, 16, 17)
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Specification