PM3350-RC データシートの表示（PDF） - PMC-Sierra

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PM3350-RC

8 PORT ETHERNET SWITCH

PMC-Sierra 

ELAN 8X10

DATA SHEET

PMC-970109

ISSUE 3

PM3350 ELAN 8 X10

8 PORT ETHERNET SWITCH

expansion port. The DMA Coprocessor operates under the control of the Switch

Processor unit to transfer packets and data at high speed between the 10BaseT ports,

the local memory and the expansion port. It also computes 32-bit IEEE Frame Check

Sequence (FCS) CRC remainders over the transferred data, allowing the Switch

Processor to filter packets with errors and generate CRCs for transmitted packets as

required.

Ethernet/IEEE 802.3 MAC Interfaces

Eight independent Ethernet/IEEE 802.3 MAC-layer interfaces are built into the ELAN

8x10 chip. These interfaces connect directly to external 10BaseT Medium Access Unit

(MAU) devices via the industry-standard 7-wire serial interface, and perform most of the

MAC-layer processing tasks required for CSMA/CD networks. In addition, each MAC

interface contains a 32-byte FIFO buffer that enhances throughput and minimizes

latency issues.

The signaling protocol used on the 7-wire serial interfaces supported by the ELAN 8x10

chip follows that required by the Advanced Micro Devices, Inc (AMD) Am7990 LANCE

device.

Expansion Port

A 32-bit parity-checked expansion port is provided to allow systems using the ELAN

8x10 to be expanded transparently from 8 to 64 ports. The expansion port supports a

peak throughput of 1 Gbit/s, and requires only a single external PAL or similar device

(to serve as a bus arbiter). Packets received on an ELAN 8x10 MAC port that are

destined for an external ELAN 8x10 are transferred over the expansion bus prior to

transmission on the designated destination port. Broadcast and multicast packets are

handled using a two-level replication scheme, in which the broadcast/multicast packet is

first transferred to all of the external ELAN 8x10s, after which it is transmitted out the

required destination ports without any further use of the expansion bus. In addition,

ELAN 8x10s interconnected via the expansion port exchange information to maintain

the distributed MIB.

Local Memory Controller

An external local memory is used for holding configuration information, MAC address

tables and statistics tables, node management data, packet buffers, and host

communication queues (if a local host CPU is present). The ELAN 8x10 integrates a

memory controller that is capable of addressing and directly driving up to 16 Mbytes of

external memory, divided into four banks of 4 Mbytes each, with decoded selects for

each bank. Independent, software programmable access times may be set for each

bank, allowing a glueless interface to a mix of EDO DRAM, EEPROM, EPROM and

ROM in the same system. An external memory timing generator may also be used if

desired. The memory controller accepts simultaneous requests from the Switch

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

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