Time slot protocol
First Claim
1. A method of operating a network having a plurality of devices coupled to a shared bus comprising the step of transmitting an epoch packet indicating the beginning of a frame wherein the frame has a plurality of time slots and wherein the epoch packet includes assignments of the time slots to the devices, and time slot offset and time slot duration information for each time slot assignment.
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Accused Products
Abstract
A computing network uses Time Division Multiplexing (TDM) to divide the time on a bus into a plurality of frames, each frame having a plurality of time slots. Each time slot is assigned no more than one of the plurality of devices within a collision domain, the assignments indicating the identity of the device permitted to transmit packets onto the network during the assigned time slot. A bus cadence unit simultaneously sends an epoch packet initiating the frame. The epoch packet contains a time slot assignment table containing the time slot assignments, the device identification, as well as a time slot offset and duration. Each device on the network is configured to measure a frame interval between repeating epoch packets. The measured frame interval is further processed in each receiving node to obtain a calibrated frame interval. The calibrated frame interval is used to accurately synchronize transmissions of data from the various devices onto the network. A time slot protocol governor in each node controls access to the bus to only the assigned time slot or slots using the calibrated frame interval to reduce or eliminate synchronization errors.
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Citations
28 Claims
- 1. A method of operating a network having a plurality of devices coupled to a shared bus comprising the step of transmitting an epoch packet indicating the beginning of a frame wherein the frame has a plurality of time slots and wherein the epoch packet includes assignments of the time slots to the devices, and time slot offset and time slot duration information for each time slot assignment.
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10. An adapter for allowing a device to access a shared bus of a network for transmitting packets during one or more time slots selected from a plurality of time slots defining a frame, said one or more time slots being assigned to said device, said adapter comprising:
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a physical interface device (PHY) unit configured to receive incoming packets from the bus, said PHY being further configured to output outgoing packets;
a media access control (MAC) unit;
a governor coupled to said physical interface device and said MAC;
a protocol unit configured to process an epoch packet during each frame, receipt by the device of said epoch packet indicating the beginning of each frame, said epoch packet having a table including (i) time slot assignments for devices on the bus, (ii) a time slot offset for each time slot assignment, and (iii) a time slot duration for each time slot assignment; and
wherein said governor is configured to control transmission of said outgoing packets onto said bus during said assigned one or more time slots in accordance with said time slot offset and duration data. - View Dependent Claims (11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22)
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23. An adapter for allowing a device to access a shared bus of a network for transmitting packets during one or more timeslots selected from a plurality of time slots defining a frame, said one or more time slots being assigned to said device for transmission, said adapter comprising:
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a physical interface device (PHY) unit configured to receive incoming packets from the bus, said PHY being further configured to output outgoing packets;
a media access control (MAC) unit;
a governor coupled to said physical interface device and said MAC;
a protocol unit configured to generate a transmission protection envelope signal based on data contained in epoch packets received at the beginning of each frame; and
wherein said governor further includes a pass gate configured to selectively prevent transmission of said outgoing packets onto the bus outside of said assigned one or more time slots in accordance with said transmission protection envelope signal. - View Dependent Claims (24)
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25. An adapter for allowing a device to access a shared bus of a network for transmitting packets during one or more time slots selected from a plurality of time slots defining a frame, said one or more time slots being assigned to said device, said network including a bus cadence unit (BCU) configured to transmit an epoch packet during said frame, said epoch packet comprising timing information and at least one reference bus attribute, said adapter comprising:
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a media access control (MAC) unit configured to receive incoming packets from the bus via a physical interface device (PHY), said MAC being further configured to output outgoing packets destined for said bus; and
a protocol unit coupled to said MAC and configured to process said incoming packets and generate at least one measured bus attribute corresponding to said reference bus attribute, said protocol unit being further configured to generate a message indicative of a condition of said bus based on said reference bus attribute and said measured bus attribute. - View Dependent Claims (26, 27, 28)
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Specification