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Электронный компонент: AL125

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Reference Only / Allayer Confidential
AL125
Advance Information
8 Port 10/100 Mbit/s Dual Speed Fast Ethernet Switch
Product Description
The AL125 is an eight-port 10/100 Mbit/s dual speed Ethernet switch. A low-cost and scalable
solution for up to 32-ports is achieved through the use of low-cost buffer memory and Allayer's
proprietary RoX-II architecture. In addition, the AL125 also supports port based and 802.1q tag
based VLAN, 802.1p priority, and multiple port aggregation trunks.
Figure 1
System Block Diagram
Supports seven 10/100 Mbit/s Ethernet ports
with RMII and one 10/100 Mbit/s Ethernet
port with MII/RMII interface
Capable of trunking up to 800 Mbit/s link
with link fail-over
Full- and half-duplex mode operation
Supports 12K MAC addresses with tag
VLAN or 16K without VLAN
Scalable design for stackable switch imple-
mentation
RoX-II expansion link supports 6.4 Gbit/s
throughput
Gigabit Ethernet ready with AL1022
Flexible prioritized queueing for multimedia
and data traffic
Layer 3/4 switching with AL3000 on RoX-II
IEEE 802.3x flow control for full-duplex
operation
Optional backpressure flow control support
for half-duplex operation
802.1p support with four priority levels
802.1q tag based and port based VLAN sup-
port, 4K VLAN table
IGMP frame trapping
Supports 64 IP multicast groups
RMON and SNMP support with the
AL300A management (MIB) device
0.25 micron, 2.5V / 3.3V CMOS technology
2.5V and 3.3V operation
Packaged in 352-pin BGA
10/100 MAC
10/100 MAC
10/100 MAC
10/100 MAC
10/100 MAC
10/100 MAC
10/100 MAC
10/100 MAC
High Speed
Switch Fabric
Switch
Controller
Address
Control
Address
Table
Buffer
Manager
Address
Table
Expansion
EEPROM
Interface
Management
Information
Expansion
Interface
AL125 Advance Information
2/2000
Reference Only / Allayer Confidential
2
AL125 Overview
The AL125 is an eight-port 10/100 ethernet switch chip with RoX-II expansion interface. The
RoX-II interface is a 3.2 Gbit/s interface (6.4 Gbit/s full-duplex). The RoX-II Bus can support up
to four switch chips and one management or router chip. Various combinations can be used for
different configurations. The maximum port configuration will be 32-port 100 Mbit/s ports or 24-
port 10/100 Mbit/s plus two Gigabit Ethernet ports, or eight gigabit ports. Higher port count
stacking configurations can be achieved with additional bridges and crossbar devices.
The RoX-II interface supports an external management device, the AL300A. SNMP and RMON
are supported through this management device. The RoX-II interface also supports Layer 3 and
Layer 4 switching provided by the AL3000. Because the AL3000 has all the AL300A functions
integrated, there is no need for the AL300A if the AL3000 is already on the RoX-II bus.
The AL125 also supports trunking applications. The chip provides two optional load balancing
schemes, explicit and dynamic. With trunking, it is possible to group up to eight full-duplex links
together to form a single 1600 Mbit/s link. The device also supports the current IEEE 802.3ad
specification.
Data received from the MAC interface is stored in the external memory buffer. The AL125
utilizes cost effective SGRAM to provide 8-Mbit or 16-Mbit of buffer memory.
The AL125 provides two flow control methods. For half-duplex operations, an optional jamming
based flow control (also known as backpressure) is available to prevent loss of data. With this
method of flow control, the switch will generate a jam signal when the receive-buffer is full. In the
full-duplex mode, the AL125 utilizes IEEE 802.3x as the flow control mechanism.
All ports support multiple MAC addresses. The switch chip supports up to 12K MAC addresses
with 4K VLAN tag or 16K MAC without VLAN through external SSRAM.
The AL125 operates only in the store and forward mode. The entire frame is checked for errors
and any frames with errors are automatically filtered and are not forwarded to the destination port.
The device also provides 64 IP multicast group addresses for IP multicast applications. The
AL125 can perform IGMP frame trapping and forward them to the CPU. This allows the CPU to
participate in the IGMP protocol and determine which ports should participate in the multicast
session.
The switch is initialized and configured by an external EEPROM. For an unmanaged switch
design, there is no need for a CPU. A parallel interface can be utilized to reprogram the EEPROM
for field reconfiguration.
The device supports port based and tagged VLAN (IEEE 802.3ac/802.1q VLAN) for workgroup
and segment switching applications.
The AL125 supports 802.1p with four levels of priority queues. Relative priority is controlled by
either programmable weighted round robin or strict priority.
The device also provides two levels of security for intrusion protection. Security can be
implemented on a per-port basis.
Other features include port monitoring and broadcast storm filtering to reduce broadcast traffic
through the switch.