A circuit, comprising: a first local controller having a first upstream port adapted to be coupled to a first local bus and adapted to receive a first local bus transmission via the first local bus, and the first local controller configured to transmit a first upstream transmission via the first upstream port; a second local controller having a second upstream port adapted to be coupled to a second local bus and adapted to receive a second local bus transmission via the second local bus, and the second local controller configured to transmit a second upstream transmission via the second upstream port; a system bus controller having a downstream port adapted to be coupled to a system bus, the system bus controller configured to generate a first downstream frame responsive to the first local bus transmission, the system bus controller configured to generate a second downstream frame responsive to the second local bus transmission, the system bus controller configured to generate a downstream aggregate frame responsive to the first downstream frame and the second downstream frame, the system bus controller configured to initiate transmission of the downstream aggregate frame at the downstream port, the system bus controller adapted to receive an upstream aggregate frame that includes a first upstream frame and a second upstream frame, the system bus controller configured to generate the first upstream transmission responsive to the first upstream frame, and the system bus controller configured to generate the second upstream transmission responsive to the second upstream frame; characterized by a translator having an input coupled to the downstream port and an output selectively coupled to one of the first upstream port and the second upstream port, the output of the translator selected responsive to an indication of an association between a selected downstream node and a respective upstream frame of the upstream aggregate frame, wherein the association between the selected downstream node and the respective upstream frame of the upstream aggregate frame is indicated by a time of reception by the downstream port of the respective upstream frame. a first local controller having a first upstream port adapted to be coupled to a first local bus and adapted to receive a first local bus transmission via the first local bus, and the first local controller configured to transmit a first upstream transmission via the first upstream port; a second local controller having a second upstream port adapted to be coupled to a second local bus and adapted to receive a second local bus transmission via the second local bus, and the second local controller configured to transmit a second upstream transmission via the second upstream port; a system bus controller having a downstream port adapted to be coupled to a system bus, the system bus controller configured to generate a first downstream frame responsive to the first local bus transmission, the system bus controller configured to generate a second downstream frame responsive to the second local bus transmission, the system bus controller configured to generate a downstream aggregate frame responsive to the first downstream frame and the second downstream frame, the system bus controller configured to initiate transmission of the downstream aggregate frame at the downstream port, the system bus controller adapted to receive an upstream aggregate frame that includes a first upstream frame and a second upstream frame, the system bus controller configured to generate the first upstream transmission responsive to the first upstream frame, and the system bus controller configured to generate the second upstream transmission responsive to the second upstream frame; characterized by a translator having an input coupled to the downstream port and an output selectively coupled to one of the first upstream port and the second upstream port, the output of the translator selected responsive to an indication of an association between a selected downstream node and a respective upstream frame of the upstream aggregate frame, wherein the association between the selected downstream node and the respective upstream frame of the upstream aggregate frame is indicated by a time of reception by the downstream port of the respective upstream frame.