US 2002/0120796 A1Published application

Maintaining remote queue using two counters in transfer controller with hub and ports

AssigneeTexas Instruments Incorporated

InventorIain Robertson

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Abstract

The data transfer apparatus and method employs two queue counters to maintain the status of a first-in-first-out buffer memory. A master count (251) indicates the number of entries available for use within the FIFO (410). New data can be allocated to the FIFO only if this master count is non-zero. This master count is decremented (401) upon allocation of new data to the FIFO. A remote count (252) stores the number of data entries stored in the FIFO. This remote count is incremented (413) upon allocation of data to the FIFO and decremented (414) upon reading data from the FIFO. A confirm decrement signal (408) from the remote count triggers an increment of the master count. This two counter technique makes better use of the available bandwidth than the prior art by not requiring a FIFO depth equal the to the data transfer latency. This technique is particularly useful in systems with delays between the data source and data destination and a mismatch of maximum data transfer rates.

Claims7

Dependent claims

A data transfer apparatus transferring data from a data source to a data destination comprising:

a first-in-first-out buffer memory having an input connected to the data source, an output connected to said data destination and a predetermined number of data entries;
a master queue counter storing a master count indicative of a number of data entries available for data storage within said first-in-first-out buffer memory, said master queue counter connected to the data source to decrement said master count upon allocation of data at said data source to be stored in said first-in-first-out buffer memory;
a remote queue counter storing a remote count indicative of a number of data entries within said first-in-first-out buffer memory currently storing data, said remote queue counter connected to said data source for incrementing said remote count upon allocation of data at said data source to be stored in said first-in-first-out buffer memory, connected to said data destination for decrementing said remote count and generating a decrement confirmation signal upon transfer of data out of said first-in-first-out buffer memory to said data destination;
and
wherein said master queue counter is further connected to said remote queue counter for incrementing said master count upon receipt of said decrement confirmation signal.

2 more elements

Dependencies are inferred from the claim text.