PM3350-SW datasheet(144/224 Pages) PMC

144 / 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

142

Default Byte Ordering

Byte 0

01243567

Byte 1

01243567

Byte 2

01243567

Byte 3

01243567

Byte 4

01243567

Byte 4

76543210

Byte 3

Byte 2

Byte 1

Byte 0

76543210

Byte 7

Byte 6

Byte 5

76543210

increasing

time

increasing

time

Ethernet/802.3 Frame

PCI Bus DWords

NextPointer

Size

AD31

AD0

Unused

Count

. . .

To permit interfacing of non-ELAN 8x10 devices via the PCI bus, this byte ordering

scheme may be selectively modified using the MWBE, MRBE, SWBE, SRBE and

EPBE byte swap enable bits in the host control register. The MWBE and MRBE bits

control the PCI bus master, and cause all data (payload and header information for

packet buffers, as well as data descriptor contents) to be statically byte-swapped prior

to writing them to or reading them from a PCI bus slave (i.e., as a result of DMA

Controller transfers). Similarly, the SWBE and SRBE bits force the PCI bus slave logic

in the ELAN 8x10 to swap data words written to and read from internal registers and

memory by an external master. Finally, the EPBE bit, if set, disables the big-endian to

little-endian conversion performed on the Ethernet frame information by the MAC

interfaces, without affecting the byte ordering of the rest of the data structures or the

packet buffer headers.

When the EPBE bit is set, the alternate byte ordering scheme used is shown in the

figure below (assuming that the MWBE, MRBE, SWBE and SRBE bits retain their

default values):

PM3350-SW Datasheet(PDF) 144 Page - PMC-Sierra, Inc

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