For a 100 Mbps operation, it is a count of the number of times an invalid code-group is received, other than the /H/ code-group. For a 1000 Mbps operation, it is a count of the number of times an invalid codegroup is received, other than the /V/ code-group. /H/ denotes a special 4b5b codeword of [802.3] 100 Mbps PCS layer (clause 24), and /V/ denotes a special 8b10b codeword of the [802.3] 1000 Mbps PCS layer (clause 36). This object is applicable for an OLT and an ONU. At the OLT, it has a distinct value for each virtual interface. Discontinuities of this counter can occur at re-initialization of the management system and at other times, as indicated by the value of the ifCounterDiscontinuityTime object of the Interface MIB module.