| 摘要 |
In an ATM cell transmission system having an ATM layer device (1), a data path interface (3) and a plurality of normal PHY (Physical) layer devices (2-0 to 2-M) according to Utopia Level 2 specification, the ATM layer device (1) comprises: a cell buffer (4); FIFO memories (5-0 to 5-M) each corresponding to each of the normal PHY layer devices (2-0 to 2-M); an output controller (5') for controlling the cell buffer (4) to output an ATM cell to be transmitted through one of the normal PHY layer devices (2-0 to 2-M) into corresponding one of the FIFO memories (5-0 to 5-M) on condition that the ATM cell is stored in the cell buffer (4) and the corresponding one of the FIFO memories (5-0 to 5-M) is not full; and a cell transmission controller (10) for performing polling of the normal PHY layer devices (2-0 to 2-M), designating a selected PHY layer device among the normal PHY layer devices (2-0 to 2-M) which have returned the HIGH level of the cell transmission allowance signal (TxClav) to the polling and whereof corresponding FIFO memories (5-0 to 5-M) are not empty, selecting one of the FIFO memories (5-0 to 5-M) corresponding to the selected PHY layer device as a next sender of cell data to be transmitted through the data path interface (3), and designating the selected PHY layer device at an end of the current transmission cycle as a next receiver of the cell data.
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