US 5,691,977 A · Virtual channel converter and VCC table access method

Abstract

In a data access device for writing into or read from a data conversion table on the basis of a clock signal extracted from a cell being transferred over a line, a clock signal generator of the invention generates a second clock signal which differs from the first clock signal extracted from an incoming cell. A write/read control unit writes data into or reads data for maintenance from the data conversion table on the basis of either the first clock signal or the second clock signal when the line is normal. In the event of the occurrence of a failure in the line, on the other hand, the write/read control circuit permits the data conversion table to be written into or read from for maintenance on the basis of the second clock signal.

Claims26

Dependent claims

A data access device for writing or reading data on the basis of a first clock signal extracted from an incoming cell being sent over a line, comprising:

storage means for storing a data conversion table;
clock signal generating means for generating a second clock signal which is different from said first clock signal extracted from the incoming cell on the line;
and
write/read control means for writing or reading data into or from said data conversion table when a request for access to said data conversion table is made by other than the line side on the basis of said second clock signal,
wherein said data conversion table for which access is requested by other than the line side can always be accessed on the basis of said second clock signal independently of whether or not failure has occurred in said line.

2 more elements

A data access device comprising:

data storage means having a plurality of data storage sections for storing input data and output data with a correspondence therebetween;
busy/free indicating information storage means having a plurality of busy/free indicating information storage sections for storing information indicating that each of said corresponding data storage sections is busy or free;
and
control means for, when a request to write data is made, storing input data and output data defined for said input data into a data storage section of said data storage means, that corresponds to a busy/free indicating information storage section of said busy/free indicating information storage means in which information indicating free is stored and for, when a request to nullify data set in said data storage means is made, making a decision as to which data storage section of said data storage means stores data identical to data to be nullified and rewriting information in that busy/free indicating information storage section of said busy/free indicating information storage means, which corresponds to the data storage section which stores the data to be nullified by information indicating free.

1 more element

A data access method for writing data into or reading data from a data conversion table on the basis of a first clock signal extracted from an incoming cell being transferred over a line, the method comprising the steps of:

writing data into or reading data from said data conversion table when a request for access to said data conversion table is made by other than the line side, on the basis of a second clock signal generated independently of said first clock signal,
wherein said data conversion table for which access is requested by other than the line side can be always accessed on the basis of said second clock signal independently on whether or not failure has occurred in said line.

A header conversion unit for converting a header of an inputted fixed length packet including a first clock into a new header, the unit comprising:

a storage means for storing a header converting table corresponding to inputted fixed length packet header information and outputted fixed length packet header information;
a clock generating means for generating a second clock different from said first clock extracted from the inputted fixed length packet;
and
a writing control signal generating means for generating and outputting a writing control signal based on said second clock when there is no inputted fixed length packet and there is a writing request to said header conversion table, terminating outputting, for a fixed period, said writing control signal when there is the inputted fixed length packet, executing header conversion with high priority to the inputted fixed length packet, and outputting the writing control signal based on said second clock until a next fixed length packet is inputted.

1 more element

A header conversion unit for converting a header of an inputted fixed length packet to a new header, the unit comprising:

first storage means having a plurality of header conversion information storage portions corresponding to an inputted fixed length packet header information and an outputted fixed length packet header information;
second used/not-used information storage means having a plurality of used/not-used information storage portions for storing information designating whether or not each header conversion information storage portion of said first storage means is used corresponding to each respective header conversion information storage portion;
and
a control means for writing to the header conversion storage portion storing not-used information in a corresponding used/not-used information storage portion when there is a header information writing request to said header conversion information storage portion.

1 more element

Dependencies are inferred from the claim text.

Virtual channel converter and VCC table access method

Life of this patent

Virtual channel converter and VCC table access method

Life of this patent

Abstract

Claims26