VSC7440 datasheet(348/444 Pages) MICROSEMI

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VCore-III System and CPU Interfaces

VMDS-10492 VSC7440 Datasheet Revision 4.2

331

The rate by which the FDMA injects frames can be shaped by using tokens. Each injection channel has

an associated token counter (FDMA_CH_INJ_TOKEN_CNT[ich]). A DCB that has the DATAL.TOKEN

field set causes the injection channel to deduct one from the token counter before the data block of the

DCB can be injected. If the token counter is at 0, the injection channel postpones injection until the

channels token counter is set to a value different from 0.

Tokens can be added to the token counter by writing the FDMA_CH_INJ_TOKEN_CNT[ich] register.

Tokens can also be added automatically (with a fixed interval) by using the dedicated token tick counter.

Setting FDMA_CH_INJ_TOKEN_TICK_RLD[ich] to a value n (different from 0) will cause one token to be

added to that injection channel every n x 200 ns.

4.7.7

Manual Mode

The decision making logic of the FDMA extraction path and/or injection paths can be disabled to give

control of the FDMA’s extraction and/or injection buffers directly to any master attached to the Shared

Bus Architecture. When operating in manual mode DCB structure, counters and most of the interrupts do

not apply.

Manual extraction and injection use hard-coded channel numbers.

•

Manual extraction mode uses FDMA channel 1 (port 54 extraction direction).

•

Manual injection mode uses FDMA channel 9 (port 54 injection direction).

To enable manual extraction, set MANUAL_CFG.XTR_ENA. The FDMA must not be enabled for FDMA

extraction when manual extraction mode is active. To enable manual injection, set

MANUAL_CFG.INJ_ENA and FDMA_CH_CFG[9].CH_INJ_CRP = 1. The FDMA must not be enabled for

FDMA injection when manual injection mode is active. Extraction and injection paths are independent.

For example, FDMA can control extraction at the same time as doing manual injection by means of the

CPU.

4.7.7.1

Manual Extraction

Extraction is done by reading one or more blocks of data from the extraction memory area. A block of

data is defined by reading one or more data words followed by reading of the extraction status word. The

extraction memory area is 16 kilobytes and is implemented as a replicated register region

MANUAL_XTR. The highest register in the replication (0xFFF) maps to the extraction status word. The

status word is updated by the extraction logic and shows the number of frame bytes read, SOF and EOF

indications, and PRUNED/ABORT indications.

Note: During frame extraction, the CPU does not know the frame length. This means that the CPU must check

for EOF regularly during frame extraction. When reading a data block from the device, the CPU can burst

read from the memory area in such a way that the extraction status word is read as the last word of the

burst.

VSC7440 Datasheet(PDF) 348 Page - Microsemi Corporation