An apparatus that allows for access to any and all registers of a central processing unit in a line replaceable unit (LRU) without a need to open the housing of the LRU is provided. The apparatus may receive write or read packets from an external device and relay the same to an LRU. The apparatus may receive state information from one or more registers of the LRU in response. The apparatus may transmit or transfer the state information to an external device. The apparatus may be used to update firmware in the LRU, for diagnostics or testing.