VSC7440 datasheet(344/444 Pages) MICROSEMI

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VCore-III System and CPU Interfaces

VMDS-10492 VSC7440 Datasheet Revision 4.2

327

DCBs are linked together by the DCB’s LLP field. The last DCB in a chain must have LLP = NULL.

Chains consisting of a single DCB are allowed.

Figure 109 •

FDMA DCB Layout

4.7.2

Enabling and Disabling FDMA Channels

To enable a channel (ch), write a valid DCB pointer to FDMA_DCB_LLP[ch] and enable the channel by

setting FDMA_CH_ACTIVATE.CH_ACTIVATE[ch]. This makes the FDMA load the DCB from memory

and start either injection or extraction.

To schedule a channel for disabling, set FDMA_CH_DISABLE.CH_DISABLE[ch]. An active channel

does not disable immediately. Instead it waits until the current data block is done, saves the status word,

and then disables.

Channels can be in one of three states: DISABLED, UPDATING, or ACTIVE. Channels are DISABLED

by default. When the channel is reading a DCB or writing the DCB status word, it is considered to be

UPDATING. The status of individual channels is available in FDMA_CH_STAT.CH_STAT[ch].

The following illustration shows the FDMA channel states.

BLOCKL [15:0]: Number of frame-data

bytes in the data block. BLOCKL does not

include offset bytes.

[31:24]: For SW

use. FDMA will not

modify.

DATAL [15:0]: Number of bytes available in

the data block associated with this DCB.

DATAL must be a complete number of words

(bit [1:0] = 00).

DATAP [31:0]: Data block pointer, this field points to the data block associated with this

DCB. DATAP must be !=NULL and must point to a word-aligned address (bit [1:0] = 00).

LLP [31:0]: Linked List Pointer, this field points to the next DCB in the list, set to NULL for

end of list. DCBs must be word-aligned, which means LLP must point to a word-aligned

address (bit [1:0] = 00).

word-address n

n + 1

n + 2

n + 3

STAT[16] SOF: Set to 1 if data block contains start of frame.

STAT[17] EOF: Set to 1 if data block contains end of frame.

STAT[18] ABORT: Abort indication.

Extraction: Set to 1 if the frame associated with the data block was aborted.

Injection: If set to 1 when FDMA loads the DCB, it aborts the frame associated with the data block.

STAT[19] PD: Pruned/Done indication.

Extraction: Set to 1 if the frame associated with the data block was pruned.

Injection: The FDMA set this to 1 when done processing the DCB. If set to 1 when FDMA loads the DCB, it

is treated as ABORT.

DATAL

STAT

DATAP

LLP

[23:18]:

Must be 0.

DATAL[16] SIG: If set to 1 when FDMA loads the DCB, the CH_CNT_SIG counter is incremented by one.

BLOCKO [31:20]: Byte offset

from beginning of the data block

to the first byte of frame-data.

DATAL[17] TOKEN: Token indication, only used during injection.

If set to 1, the FDMA uses one token (CH_INJ_TOKEN_CNT) when injecting the contents of the DCB. If the

token counter is 0 when loading the DCB, then injection is postponed until tokens are made available.

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