PM3350 Datasheet, PDF (186/224 Pages) PMC-Sierra, Inc – 8-Port 10 Mbit/s Switch

ELAN 8X10
DATA SHEET
PMC-970109
ISSUE 3
PM3350 ELAN 8 X10
8 PORT ETHERNET SWITCH
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
register
• 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:
PROPRIETARY AND CONFIDENTIAL TO PMC-SIERRA, INC., AND PMC-SIERRA, INC. CUSTOMERS ONLY
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