IPC분류정보
국가/구분 |
United States(US) Patent
등록
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국제특허분류(IPC7판) |
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출원번호 |
US-0751568
(2000-12-29)
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발명자
/ 주소 |
- Moyal, Yehuda
- Levi, Yehezkel
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출원인 / 주소 |
- Cisco Systems O.I.A. (1988) Ltd.
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대리인 / 주소 |
Schwegman, Lundberg, Woessner & Kluth, P.A.
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인용정보 |
피인용 횟수 :
9 인용 특허 :
11 |
초록
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A novel and useful mechanism of synchronizing and aligning a plurality of data streams. The invention comprises a plurality of sync machines and an alignment circuit which in combination function to synchronize and align multiple variable length cell streams. Each sync machine is operative to contro
A novel and useful mechanism of synchronizing and aligning a plurality of data streams. The invention comprises a plurality of sync machines and an alignment circuit which in combination function to synchronize and align multiple variable length cell streams. Each sync machine is operative to control the output clocking of a corresponding FIFO queue. The data stream output of each FIFO queue is monitored by a sync machine and all the sync machines are coupled to the alignment circuit. In operation, the sync machines synchronize to the cells by searching for the error checks sequence (ECS) at the end of each cell. Upon synchronization being achieved for all the data streams, the alignment circuit causes each sync machine to freeze its respective FIFO until the ECS arrives on the data stream most delayed in time. Once the ECS is received on the slowest data stream, the alignment circuit releases the hold and consequently the FIFOs are released by the sync machines.
대표청구항
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1. A method of aligning a plurality of data streams, each data stream comprising a series of cells, each cell comprising a data portion and an error check sequence (ECS), said method comprising the steps of:synchronizing on each data stream independently by determining the start and end of each cell
1. A method of aligning a plurality of data streams, each data stream comprising a series of cells, each cell comprising a data portion and an error check sequence (ECS), said method comprising the steps of:synchronizing on each data stream independently by determining the start and end of each cell in accordance with its length, and generating a synchronization pulse upon the detection of the ECS in each cell;generating a hold signal upon the generation of a synchronization pulse produced in response to the last of said plurality of data streams to achieve synchronization;suspending the flow of each of said data streams in response to the assertion of said hold signal and upon the detection of the subsequent ECS within each particular data stream; andresuming the flow of each of said data streams simultaneously upon the detection of the ECS associated with the most delayed in time data stream. 2. The method according to claim 1, wherein said step of synchronizing is performed with the knowledge of a fixed length known a priori. 3. The method according to claim 1, wherein said step of synchronizing is performed using a length that is variable on a per cell basis and that is common at any one time across all data streams in parallel. 4. The method according to claim 1, wherein said step of synchronizing is performed using a length that is provided on a per cell basis by an external entity. 5. The method according to claim 1, wherein said synchronization pulse is generated only after the detection of a predetermined number of correct error check sequences. 6. The method according to claim 1, wherein said step of suspending the flow of each of said data streams comprises suspending the clock input to a first in first out (FIFO) queue associated with each data stream. 7. The method according to claim 1, wherein said step of resuming the flow of each of said data streams comprises resuming the clocking of a plurality of first in first out (FIFO) queues, each FIFO queue associated with a single data stream. 8. An alignment apparatus of aligning a plurality of data streams, each data stream comprising a series of cells, each cell comprising a data portion and an error check sequence (ECS), comprising:a plurality of synchronization machines, each synchronization machine adapted to receive one of said data streams, determine the start and end of each cell in accordance with its length, and to generate a synchronization pulse upon the detection of the ECS in each cell, wherein each synchronization machine comprises suspension means adapted to suspend the flow of a particular data stream upon the assertion of a hold signal and the detection of the subsequent ECS within the particular data stream and adapted to resume the flow of said data stream in response to the de-assertion of said hold signal;an alignment mechanism operative to assert said hold signal upon the generation of a synchronization pulse produced in response to the last of said plurality of data streams to achieve synchronization, and to de-assert said hold signal, thus causing the simultaneous resumption of the flows of each said data stream, upon the detection of the ECS associated with the most delayed in time data stream. 9. The apparatus according to claim 8, wherein each said synchronization machine is adapted to determine the start and end of each cell utilizing a fixed length known a priori. 10. The apparatus according to claim 8, wherein each said synchronization machine is adapted to determine the start and end of each cell using a length that is variable on a per cell basis and which is common at any moment in time across all data streams in parallel. 11. The apparatus according to claim 8, wherein each said synchronization machine is adapted to determine the start and end of each cell using a length that is provided on a per cell basis by an external entity. 12 .The apparatus according to claim 8, wherein each said synchronization machine is adapted to generate said synchronization pulse only after the detection of a predetermined number of correct error check sequences. 13. The apparatus according to claim 8, wherein said synchronization machine is adapted to suspend the flow of each data stream by suspending the clock input to a first in first out (FIFO) queue associated with each data stream. 14. The apparatus according to claim 8, wherein said synchronization machine is adapted to resume the flow of each data stream by resuming the clocking of a plurality of first in first out (FIFO) queues, each FIFO queue associated with a single data stream. 15. A data communications system for processing an input data stream as a plurality of data streams, each data stream comprising a series of cells, each cell comprising a data portion and an error check sequence (ECS), comprising:a receive line card adapted to receive and split said input data stream into a plurality of data streams;a plurality of processing cards, each processing card operative to process one of said data streams;a transmit line card operative to align and combine the plurality of data streams output of said processing cards into a single output data stream, said transmit line card comprising alignment means operative to:synchronize on each data stream independently by determining the start and end of each cell in accordance with its length, and generating a synchronization pulse upon the detection of the ECS in each cell;generate a hold signal upon the generation of a synchronization pulse produced in response to the last of said plurality of data streams to achieve synchronization;suspend the flow of each of said data streams in response to the assertion of said hold signal and upon the detection of the subsequent ECS within each particular data stream; andresume the flow of each of said data streams simultaneously upon the detection of the ECS associated with the most delayed in time data stream. 16. The system according to claim 15, wherein each data stream is synchronized using a fixed length known a priori. 17. The system according to claim 15, wherein each data stream is synchronized using a length that is variable on a per cell basis and that is common at any one time across all data streams in parallel. 18. The system according to claim 15, wherein each data stream is synchronized using a length that is provided on a per cell basis by an external entity. 19. The system according to claim 15, wherein said synchronization pulse is generated only after the detection of a predetermined number of correct error check sequences. 20. The system according to claim 15, wherein the flow of each of said data streams is suspended by suspending the clock input to a first in first out (FIFO) queue associated wvith each data stream. 21. The system according to claim 15, wherein the flow of each of said data streams is resumed by resuming the clocking of a plurality of first in first out (FIFO) queues, each FIFO queue associated with a single data stream.
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