A read-write value that indicates the mode of operation of the 1000BASE-PX PHY optional FEC Sublayer for Forward error correction see [802.3ah] clause 65.2). A GET operation returns the current mode of operation the PHY. A SET operation changes the mode of operation of the PHY to the indicated value. unknown(1) value is assigned in initializing, for non FEC support state or type not yet known. disabled(2) value is assigned when Sublayer operating in disabled mode. enabled(3) value is assigned when Sublayer operating in FEC mode. writing can be done all the time.