2.7 DVM messages

The RN-Fs in the CCN-502 that support Distributed Virtual Memory (DVM) messages can send DVM requests and receive DVM snoops. In addition, RN-Is that include a System Memory Management Unit (SMMU) and connect to an RN-I bridge that supports DVMs, can receive DVM snoops.

A DVM message from an RN-F is sent to the MN and then the MN forwards it as a snoop to the participating RNs. The MN is also responsible for collecting the individual snoop responses and sending a single response back to the RN-F, that originated the DVM message transaction. The DVM Domain Control register in the MN includes the list of RNs that are destinations for DVM snoops.

Note:

  • An RN that issues DVM messages must also be able to receive DVM messages. If this requirement is violated, the system must not rely on the DVM message causing any DVM snoops.
  • An RN-F can issue only one outstanding DVMOp(Sync).
  • The CCN-502 can send a maximum of four outstanding DVM transactions to an RN-F.

For more information about DVM messages, see the ARM® AMBA® 5 CHI Architecture Specification.

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