PM3350-SW datasheet(186/224 Pages) PMC

186 / 224 page

ELAN 8X10

PM3350 ELAN 8 X10

DATA SHEET

PMC-970109

ISSUE 3

8 PORT ETHERNET SWITCH

PROPRIETARY AND CONFIDENTIAL TO PMC-SIERRA, INC., AND PMC-SIERRA, INC. CUSTOMERS ONLY

184

The RPCIM must arbitrate with the other internal DMA channels that can initiate PCI

write transactions for access to a shared hardware resource: the PCI Master Write

FIFO (MWF FIFO) that is part of the internal PCI Bus Interace Unit (PCI_BIU). The

arbiter for access to the MWF FIFO is internal to the RPCIM logic. The grant for the

write interface, `rwr_gt', is set on the cycle before the RPCIM writes the command word

in the MWF FIFO.

Upon writing the last word of the command/address/data into the MWF FIFO for a given

transaction, the following occurs concurrently:

•

the rpcim_done line is asserted (this maps to one of the interrupt lines on the

PM3351 Switch Processor).

•

rwr_gt is deasserted; this allows another DMA channel to perform PCI write

transactions.

On the PCI bus the write transaction will appear as a single burst transaction of

"BYTECOUNT" bits.

The Switch Processor takes the rpcim_done interrupt:

•

Switch Processor does a clr_rpcim_done flip at beginning of the interrupt

routine, which deasserts the rpcim_done interrupt and clears state of the RPCIM

module (returns the internal state machine to IDLE and resets data FIFO write

and read pointers).

•

if (the Switch Processor wants to continue the DMA transfer) the Switch

Processor firmware computes the next PCI address and writes the new

ByteWriteAddress into RPCIADDR:

• ByteWriteAddress = ByteWriteAddress + sizeof_last_BYTECOUNT

(which is probably 64);

•

Switch Processor firmware writes data for the next transfer to the RPCIDATA

•

Switch Processor writes the RPCIMD register with BYTECOUNT of new

transaction.

Outline of RPCIM memory/configuration READ transactions:

Although there is only one hardware mode of operation for performing read transactions

the Switch Processor firmware can determine how transactions of larger than 64 bytes

are handled:

PM3350-SW Datasheet(PDF) 186 Page - PMC-Sierra, Inc

PM3350-SW Datasheet(HTML) 186 Page - PMC-Sierra, Inc

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