VSC7440 datasheet(75/444 Pages) MICROSEMI

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Functional Descriptions

VMDS-10492 VSC7440 Datasheet Revision 4.2

Blocks are located back-to-back in the VCAP memory space. Block 0 is assigned addresses 0 through

1,023; block 1 is assigned addresses 1,024 though 2,047; and so on. Prioritizing of rules based on

address still applies when multiple blocks are assigned to the same VCAP.

To simplify software development, all blocks assigned to the same VCAP should be allocated as one

consecutive region of addresses in memory. After a block of VCAP resources is allocated to a VCAP, it

cannot be reallocated. Resource assignment must be done during startup before the VCAPs are

enabled.

After reset, all VCAP resources default to unallocated power-down mode. To allocate a block from the

shared pool, write block index to VCAP_CORE_IDX.CORE_IDX, then map it to a specific interface by

writing VCAP_CORE_MAP.CORE_MAP. For more information, see the register description for encoding

of owners.

3.12.1.4 Bringing Up VCAP

The contents of the VCAP are unknown after reset. Software must initialize all addresses of the VCAP to

disabled entry and all-zeros in action and counter before enabling lookups.

The default rules of the VCAPs must also be initialized. After lookup is enabled for the VCAPs, default

rules are triggered and applied to frames.

Some VCAPs implement resource sharing. As a result, software must allocate resources as part of

VCAP bring up.

For more information about default addresses rules and resource allocation, see Individual VCAPs,

page 59.

3.12.2

Wide VCAP Entries and Actions

Some VCAPs support entries and actions that are wider than a single address in the VCAP memory. The

size of an entry or action is described as Xn, where n is the number of addresses that is taken up in

memory. When programming an X2 or larger entry or action, addresses are written one by one until the

entire entry or action is written to VCAP memory.

A rule consists of one entry and one action. The size of the rule is described as Xn where n is the largest

of entry or action widths. For example, a rule consisting of an X2 entry and an X4 action is considered to

be an X4 rule. The entry and action must start at the same address, so that address offset 0 for both

entry and action is located at the same address inside the VCAP memory.

When programming a rule where the action is wider than the entry, entry addresses exceeding the size of

the entry must be disabled. When the entry is wider than the action, action addresses exceeding the size

of the action must be set to zeros.

The starting address of an Xn rule must be divisible by n. This means that X1 rules may be placed at any

address, X2 rules may only placed at even addresses, X4 rules may only be placed at addresses

divisible by 4, and so on. During move-operations this puts a restriction on the distance that rules are

moved. In other words, when performing move-operation on a region of VCAP memory that contains

rules of X2 or larger size, the rules must still be at legal addresses after the move.

When a rule is matched by a key, the counter at address offset 0 is incremented.

When writing an X2 or larger rule, software must start with the highest address and end with the lowest

address. This is needed so that rules are not triggered prematurely during writing. When disabling rules,

software must start by disabling the lowest address. This is automatically handled when using the

initialization operation for disabling rules.

3.12.2.1 Type-Group Fields

A special type-group field is required to differentiate rules when a VCAP supports different sized entries

or actions. The type-group is not part of the entry/action description. Software has to manually lookup

and insert type-group field into entry/action data when writing rules to VCAP memory.

The type-group field is placed at the low bits of the entry and/or action. The value and width of the type-

group field differs between VCAPs and depends on the entry/action size of and the address offset into

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