Communication Infrastructure

1. The 3 interconnection Networks

The TSAR architecture defines three logically independent VCI compliant networks, that are fully separated for dead-lock prevention :

• The Direct Network implements the 40 bits TSAR physical address space that is visible by the software. It transports the direct READ, WRITE, LL, & SC transactions from any VCI initiator (typically a L1 cache controller or another hardware coprocessor with a DMA capability) to any VCI target (typically a memory cache controller, or a memory mapped peripheral).

• The Coherence Network implements a separated 40 bits physical address space, used to transport the coherence transactions : MULTI_UPDATE, MULTI_INVAL, BROADCAST_INVAL (from memory cache controllers to L1 cache controllers) and CLEANUP (from the L1 cache controllers to the memory cache controllers). This address space is not visible by the software.

• The External Network implements a 34 bits physical address space.This network transports the PUT and GET transactions from the memory cache controller to the external RAM controller, in case of MISS or cache line replacement in the memory cache. This address space is not visible by the software.

2. VCI Initiators & Targets Indexing

As a given hardware component can have several VCI ports (for example the L1 cache has two VCI initiator ports to the direct network, and to the coherence network), each VCI port should have a different identifier. In the specific case of the TSAR architecture, a VCI target or initiator component will never have several VCI port of the same type (Initiator type or Target type) on the same network. Therefore, each hardware component has – for sake of simplicity - an absolute identifier that is defined by three indexes :

• X_INDEX is the cluster X-coordinate.
• Y_INDEX is the cluster Y-coordinate.
• LOCAL_INDEX is the local index inside the cluster.