A10.3 Attributes of the CHI master interface

The table lists the possible values for the read and write issuing capabilities if the processor includes four cores.

nNumber of cores.
m1 if the processor is configured for the ACP interface, 0 if it is not.
w(write issuing capability)+1.

Table A10-3 Attributes of the CHI master memory interface

Attribute Value Comments

Write issuing capability

Configuration dependent

The maximum number of writes varies, depending on the configuration of the processor:

  • The number of cores.
  • The presence of the L2 cache.

If no L2 cache is configured:

One core5 outstanding writes.
2-4 cores8 outstanding writes.

If an L2 cache is configured:

One core7 outstanding writes.
2-4 cores10 outstanding write.

A cluster with four cores, with L2 cache, can issue 10 outstanding transactions. A processor with one core, without L2 cache, can issue five outstanding transactions.

All outstanding transactions use a unique ID.

Read issuing capability

8n + 4m + 1

8 for each core in the cluster including up to:

  • 8 data linefills.
  • 4 Non-cacheable or Device data reads.
  • 1 Non-cacheable TLB page-walk read.
  • 3 instruction linefills.
  • 5 coherency operations.
  • 1 barrier operation.
  • 8 DVM messages.

If an ACP is configured, up to 4 ACP linefill requests can be generated. 1 barrier operation is generated from the cluster.

Exclusive thread capability

n Each core can have 1 exclusive access sequence in progress.

Transaction ID width

8 The ID encodes the source of the memory transaction. See A9.5 Attributes of the ACE master interface.

Transaction ID capability

8n + 4m + w + 1

8 for each core in the cluster in addition to:

  • 4 for the ACP interface.
  • 1 for barriers.
  • 6 to 11 writes, depending on the write issuing capability.

Unlike in configurations with AXI or ACE, there is never any ID reuse in CHI implementations, regardless of the memory type.

There is no fixed mapping between CHI transaction IDs and cores. Some transaction IDs can be used for either reads or writes.

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