VSC7440 datasheet(349/444 Pages) MICROSEMI

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VCore-III System and CPU Interfaces

VMDS-10492 VSC7440 Datasheet Revision 4.2

332

Figure 112 •

Extraction Status Word Encoding

The extraction logic updates the extraction status word while the CPU is reading out data for a block.

Prior to starting a new data block, the CPU can write the two least significant bits of the BLOCKO field.

The BLOCKO value is stored in the extraction logic and takes effect when the new data block is started.

Reading the status field always returns the BLOCKO value that applies to the current data block. Unless

written (before stating a data block), the BLOCKO is cleared, so by default all blocks have 0 byte offset.

The offset can be written multiple times; the last value takes effect.

The CPU can abort frames that it has already started to read out by writing the extraction status field with

the ABORT field set. All other status-word fields will be ignored. This causes the extraction logic to

discard the active frame and remove it from the queuing system.

Reading of block data does not have to be done in one burst. As long as the status word is not read,

multiple reads from the extraction region are treated as belonging to the same block.

4.7.7.2

Manual Injection

Injection is done by writing one or more blocks of data to the injection memory area. A block of data is

defined by writing an injection status word followed by writing one or more data words. The injection

memory area is 16 kilobytes and is implemented as a replicated register region MANUAL_INJ. The first

following:

•

Number of bytes to be injected

•

Optional byte offset before injection data

•

SOF and EOF indications

•

Optional ABORT indication

Note: In general, it makes sense to inject frames as a single large block of data (containing both SOF and

EOF). However, because offset/length can be specified individually for each block, injecting frames

through several blocks is useful when compensating for offset/word misalignment. For example, when

building a frame from different memory regions in the CPU main memory.

[31:20]

[15:0]

BLOCKL: The amount of frame data (bytes) that

has been read in this block. The CPU might have

read more data than this, only valid frame data

(including Extraction Header) is counted here.

SOF: Start of frame, set if this block contains

start of a frame.

EOF: End of frame, set if this block contains end

of a frame.

ABORT: Set if this frame has been aborted by

the Queuing System. Write ‘1’ to discard the

remainder of the active frame.

PD: Pruned indication, set if the frame has been

pruned to less than original length.

BLOCKO: The amount of dummy bytes (non-frame

data) read before start of frame data.

BLOCKL

BLOCKO

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