VSC7440 datasheet(345/444 Pages) MICROSEMI

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VCore-III System and CPU Interfaces

VMDS-10492 VSC7440 Datasheet Revision 4.2

328

Figure 110 •

FDMA Channel States

A channel that has FDMA_DCB_LLP[ch].DCB_LLP==NULL when going from ACTIVE to UPDATING

disables itself instead of loading a new DCB. After this it can be re-enabled as previously described.

Extraction channels emit an INTR_LLP-event when loading a DCB with LLP==NULL. Injection channels

emit an INTR_LLP-event when saving status for a DCB that has the LLP==NULL.

Note: Extraction channel running out of DCBs during extraction is a problem that software must avoid. A

hanging extraction channel will potentially be head-of-line blocking other extraction channels.

It is possible to update an active channels LLP pointer and pointers in the DCB chains. Before changing

pointers software must schedule the channel for disabling (by writing

FDMA_CH_DISABLE.CH_DISABLE[ch]) and then wait for the channel to set

FDMA_CH_SAFE.CH_SAFE[ch]. When the pointer update is complete, soft must re-activate the channel

by setting FDMA_CH_ACTIVATE.CH_ACTIVATE[ch]. Setting activate will cancel the deactivate-request,

or if the channel has disabled itself in the meantime, it will re activate the channel.

Note: The address of the current DCB is available in FDMA_DCB_LLP_PREV[ch]. This information is useful

when modifying pointers for an active channel. The FDMA does not reload the current DCB when re-

activated, so if the LLP-field of the current DCB is modified, then software must also modify

FDMA_DCB_LLP[ch].

Setting FDMA_CH_CFG[ch].DONEEOF_STOP_ENA disables an FDMA channel and emits LLP-event

after saving status for DCBs that contains EOF (after extracting or injecting a complete frame). Setting

FDMA_CH_CFG[ch].DONE_STOP_ENA disables an FDMA channel and emits LLP-event after saving

status for any DCB.

4.7.3

Channel Counters

The FDMA implements three counters per channel: SIG, DCB, and FRM. These counters are accessible

through FDMA_CH_CNT[ch].CH_CNT_SIG, FDMA_CH_CNT[ch].CH_CNT_DCB, and

FDMA_CH_CNT[ch].CH_CNT_FRM, respectively. For more information about how to safely modify

these counters, see the register descriptions.

•

The SIG (signal) counter is incremented by one each time the FDMA loads a DCB that has the

DATAL.SIG bit set to 1.

DISABLED

UPDATING

ACTIVE

Update STAT word at address

ICPU_CFG::FDMA_DCB_LLP_PREV[ch] + 0xC.

Disable when DCB.LLP == NULL or

user requested DISABLE of channel.

Enable when user requested

ACTIVATE of channel.

Load DCB from address

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