Optical transceiver and method of controlling the same

A method of controlling an optical transceiver including an optical transmission circuit configured to convert a first electrical signal into a first optical signal, an optical reception circuit configured to convert a second optical signal into a second electrical signal, a first processing unit configured to control a section of the optical transmission circuit and including a first memory having a first memory region, the first memory region including a first plurality of Management Data Input/Output (MDIO) registers that store data for controlling said optical transmission circuit section, a second processing unit configured to control a section of the the optical reception circuit and including a second memory having a second memory region, the second memory region including a second plurality of MDIO registers that store data for controlling said optical reception circuit section, a MDIO communication bus connected to the first processing unit and the second processing unit and capable of being electrically connected to an external MDIO communication bus of an external apparatus, and a signal line for sending a selection signal from the first processing unit to the second processing unit, the method comprising:

• receiving a MDIO frame from the external apparatus through the external MDIO communication bus and the MDIO communication bus, the MDIO frame having an operation (OP) code set to “00h” and a MDIO register address set in a payload thereof,
• setting the selection signal to a first level when the first memory region includes a MDIO register designated by the MDIO register address, and setting the selection signal to a second level when the second memory region includes the MDIO register designated by the MDIO register address,
• receiving another MDIO frame from the external apparatus through the external MDIO communication bus and the MDIO communication bus, the another MDIO frame having an OP code set to other than “00h”, and
• responding to the another MDIO frame by the first processing unit when the selection signal is at the first level, and alternatively by the second processing unit when the selection signal is at the second level.