LAN9313 datasheet(57/398 Pages) SMSC

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Three Port 10/100 Managed Ethernet Switch with MII

Datasheet

SMSC LAN9313/LAN9313i

Revision 1.2 (04-08-08)

DATASHEET

Chapter 6 Switch Fabric

6.1

Functional Overview

At the core of the LAN9313/LAN9313i is the high performance, high efficiency 3 port Ethernet switch

fabric. The switch fabric contains a 3 port VLAN layer 2 switch engine that supports untagged, VLAN

tagged, and priority tagged frames. The switch fabric provides an extensive feature set which includes

spanning tree protocol support, multicast packet filtering and Quality of Service (QoS) packet

prioritization by VLAN tag, destination address, port default value or DIFFSERV/TOS, allowing for a

range of prioritization implementations. 32K of buffer RAM allows for the storage of multiple packets

while forwarding operations are completed, and a 1K entry forwarding table provides room for MAC

address forwarding tables. Each port is allocated a cluster of 4 dynamic QoS queues which allow each

queue size to grow and shrink with traffic, effectively utilizing all available memory. This memory is

managed dynamically via the buffer manager block within the switch fabric. All aspects of the switch

fabric are managed via the switch fabric configuration and status registers (CSR), which are indirectly

accessible via the system control and status registers.

The switch fabric consists of four major block types:

Switch Fabric CSRs - These registers provide access to various switch fabric parameters for

configuration and monitoring.

10/100 Ethernet MACs - A total of three MACs are included in the switch fabric which provide basic

10/100 Ethernet functionality for each switch fabric port.

Switch Engine (SWE) - This block is the core of the switch fabric and provides VLAN layer 2

switching for all three switch ports.

Buffer Manager (BM) - This block provides control of the free buffer space, transmit queues, and

scheduling.

Refer to Figure 2.1 Internal LAN9313/LAN9313i Block Diagram on page 19 for details on the

interconnection of the switch fabric blocks within the LAN9313/LAN9313i.

6.2

Switch Fabric CSRs

The switch fabric CSRs provide register level access to the various parameters of the switch fabric.

Switch fabric related registers can be classified into two main categories based upon their method of

access: direct and indirect.

The directly accessible switch fabric registers are part of the main system CSRs of the

LAN9313/LAN9313i and are detailed in Section 13.1.5, "Switch Fabric," on page 192. These registers

provide switch fabric manual flow control (Ports 0-2), data/command registers (for access to the indirect

switch fabric registers), and switch MAC address configuration.

The indirectly accessible switch fabric registers reside within the switch fabric and must be accessed

indirectly via the Switch Fabric CSR Interface Data Register (SWITCH_CSR_DATA) and Switch Fabric

CSR Interface Command Register (SWITCH_CSR_CMD), or the set of Switch Fabric CSR Interface

Direct Data Register (SWITCH_CSR_DIRECT_DATA). The indirectly accessible switch fabric CSRs

provide full access to the many configurable parameters of the switch engine, buffer manager, and

each switch port. The switch fabric CSRs are detailed in Section 13.3, "Switch Fabric Control and

Status Registers," on page 253.

For detailed descriptions of all switch fabric related registers, refer to Chapter 13, "Register

Descriptions," on page 146.

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