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Functional Descriptions

VMDS-10488 VSC7511 Datasheet Revision 4.2

Initiating another operation before the UPDATE_SHOT field is cleared is not allowed. The delay between

setting the UPDATE_SHOT field and the clearing of that field depends on the type of operation and the

traffic load on the VCAP.

By setting the fields UPDATE_ENTRY_DIS, UPDATE_ACTION_DIS, and/or UPDATE_CNT_DIS in the

VCAP_UPDATE_CTRL register the writing of the TCAM, action, and/or the counter entry can be

disabled.

Copying a VCAP entry from the TCAM/RAM to the cache is done in a similar fashion by setting

VCAP_UPDATE_CTRL.UPDATE_CMD to copy from TCAM/RAM to the cache. Note that due to internal

mapping of the entry data and mask data, the values that are read back from the TCAM cannot always

match with the values that were originally written to the TCAM. The internal mapping that happens is

listed in the following table. There are differences, because a masked 1 is read back as a masked 0,

which is functionally the same.

If an entry match is not found during a lookup for a given frame, a default action is selected by the VCAP.

Default actions and counter values are copied between the cache and the action RAM similar to a regular

VCAP entry. The default actions are stored in the RAM right below the last regular action entry; for

example, VCAP IS2 has 256 regular entries, so the first default action in VCAP IS2 is stored at address

256, the second at address 257, and so on. For more information about the number of regular VCAP

entries in each VCAP, see Table 69, page 96. When a default action is copied from the cache to the

RAM, VCAP_UPDATE_CTRL.UPDATE_ENTRY_DIS must be set to disable the update of the TCAM. If

updating of the TCAM is not disabled, the operation may overwrite entries in the TCAM.

The cache can be cleared by setting VCAP_UPDATE_CTRL.CLEAR_CACHE. This sets all replications

of VCAP_ENTRY_DAT, VCAP_MASK_DAT, VCAP_ACTION_DAT, VCAP_CNT_DAT, and

VCAP_TG_DAT to zeros. The CLEAR_CACHE field is automatically cleared by hardware when the

cache is cleared.

3.8.7

Advanced VCAP Operations

The VCAP supports a number of advanced operations that allow easy moving and removal of entries and

actions during frame traffic.

3.8.7.1

Moving a Block of Entries and Actions

A number of entries and actions can be moved up or down by several positions in the TCAM and RAM.

This is done using the VCAP_UPDATE_CTRL and VCAP_MV_CFG registers.

A Move operation is performed by:

•

Setting VCAP_UPDATE_CTRL.UPDATE_ADDR equal to the address of the entry with the lowest

address, among the entries that must be moved.

•

Setting VCAP_MV_CFG.MV_SIZE to the number of entries that must be moved; n + 1 entries are

moved.

•

Setting VCAP_MV_CFG.MV_NUM_POS to the number of positions the entries must be moved. The

entries are moved n positions up or down.

•

Setting UPDATE_ENTRY_DIS, UPDATE_ACTION_DIS, and/or UPDATE_CNT_DIS to only move

some parts of the VCAP entry.

•

Setting VCAP_UPDATE_CTRL.UPDATE_CMD to move up (decreasing addresses) or move down

(increasing addresses).

•

Initiating the Move operation by setting VCAP_UPDATE_CTRL.VCAP_UPDATE_SHOT.

Table 72 •

Internal Mapping of Entry and Mask

Written Entry

Written Mask

Description

Read Entry

Read Mask

Match-0

Match-Any

Match-1

Match-Any

VSC7511 Datasheet(PDF) 114 Page - Microsemi Corporation

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