ATM header conversion circuit and method

An ATM header conversion circuit comprising:

• entry data storage means for storing ATM header data, which remain unchanged before and after conversion, as entry data in a state associated with first and second addresses paired;
• full collation means for fully collating inputted header data with said ATM header data, stored in said entry data storage means, at each of said pairs of first and second addresses to output a collation result at each of said pairs of first and second addresses;
• address extraction means for extracting, on the basis of said collation result at each of said pairs of first and second addresses, said first and second addresses in said entry data storage means at which said collation result shows coincidence;
• converted ATM header storage means for previously storing said ATM header data after conversion in a state associated with said first and second addresses in said entry data storage means;
• and
• readout means for selecting one of said first and second addresses extracted in said address extraction means on the basis of a direction of the ATM header conversion to read out said ATM header data at the selected address from said converted ATM header storage means.

An ATM header conversion method for an optical subscriber transmission system, comprising the steps of:

• storing, as entry data, first and second ATM header data paired at each of a plurality of addresses;
• partially collating inputted header data with one of said first and second ATM header data stored by said storing step for each address on the basis of a designation signal representative of a collation position of said ATM header data being converted;
• outputting a collation result for each address;
• extracting, on the basis of the collation result for each address, an address, stored by said storing step, at which the collation result shows coincidence;
• and
• outputting, as converted ATM header data, the other of said first and second ATM header data at said address extracted by said extracting step.

An ATM header conversion method for an optical subscriber transmission system, comprising the steps of:

• storing ATM header data, which remain unchanged before and after conversion, as entry data in a state associated with first and second addresses paired;
• fully collating inputted header data with said ATM header data, stored by said storing step, at each of said pairs of first and second addresses to output a collation result at each of said pairs of first and second addresses;
• extracting, on the basis of said collation result at each of said pairs of first and second addresses, said first and second addresses storied by said storing step at which said collation result shows coincidence;
• storing in advance, in a converted ATM header storage means, said ATM header data after conversion in a state associated with said first and second addresses stored by said storing step;
• and
• selecting one of said first and second addresses extracted by said extracting step on the basis of a direction of the ATM header conversion to read out said ATM header data at the selected address from said converted ATM header storage means.