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All CHI transactions require a TgtID.
For addressable requests, the TgtID is determined by the System Address Map (SAM). For responses, the TgtID is determined based on the Node Identifier (NodeID) of the requester, which is sent as a SrcID on a request. The coherent interconnect uses this TgtID to route packets from source to destination.
For the CCN-502, all RNs must generate the TgtID and present it on the CHI interface. An address map therefore is located in every node capable of generating a CHI addressable request. This includes the following:
RNs because addressable requests are sent to HNs and MN.
HNs because addressable requests are sent to the SNs, for example, memory controllers.
ACE and AXI masters are excluded from this requirement, because the RN SAM is implemented in the RN-I bridge.