| 摘要 |
PROBLEM TO BE SOLVED: To provide a physical layer device with a test circuit constituted, so as to be capable of performing tests by the physical layer device alone and capable of realizing shortening of the test time and the reduction of test cost. SOLUTION: The physical layer device 21 is equipped with a link layer interface 2, a physical layer logic circuit 3 and boards 4-6 and further is equipped with a testing link layer circuit 22 in the inside, a testing physical layer logic circuit 23 and switches 24-26. At testing, the ports 4-6 are externally connected by a cable 27 and the contacts of the switches 24-26 are changed over. As a result of this constitution, the physical layer logic circuit 3 is connected to the a testing link layer circuit 22, and the boards 5, 6 are connected to the testing physical layer logic circuit 23.
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