Reference Only / Allayer Confidential
AL15
Advance Information
Five-Port Low Cost 10/100 Switch With RMII
Product Description
The AL15 is an five-port 10/100 Mbit/s dual speed Ethernet switch. A low-cost Fast Ethernet
switch can be implemented using the AL15 with low-cost SGRAM.
Figure 1
System Block Diagram
Supports five 10/100 Mbit/s Ethernet
ports with RMII interface
Capable of trunking up to 500 Mbit/s
link
Full- and half-duplex mode operation
Speed auto-negotiation through MDIO
Built-in storage of 1K MAC addresses
expandable up to 17K
Design to utilize low-cost SGRAM
Serial EEPROM interface for low-cost
system configuration
Automatic source address learning
Secure mode traffic filtering
Broadcast storm control
Port monitoring support
IEEE 802.3x flow control for full-duplex
operation
Optional backpressure flow control support
for half-duplex operation
Supports store-and-forward mode switching
VLAN support
0.35 micron, 3.3V CMOS technology
Packaged in 208-pin PQFP
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
AL15 Advance Information
2/2000
Reference Only / Allayer Confidential
2
AL15 Overview
The AL15 provides five 10/100 Mbit/s Ethernet ports. Each port supports both 10 and 100
Mbit/s data rate. The operation mode is auto-negotiated by the PHY. All ports are full-duplex
capable. The device also supports VLAN for workgroup and segment switching applications.
Data received from the MAC interface is stored in the external memory buffer. The AL15 utilizes
cost effective SGRAM to provide 8-Mbit or 16-Mbit of buffer memory.
During transmission, the data is obtained from the buffer memory and routed to the destination
port's output buffer. If a collision occurs during a half-duplex operation, the MAC control will back
off and retransmit in accordance to the IEEE 802.3 specification.
The AL15 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 and the
sending station will not start to transmit until the line is clear. In the full-duplex mode, the AL15
utilizes IEEE 802.3x as the flow-control mechanism.
All ports support multiple MAC addresses. The switch chip supports 1K MAC addresses internally
and are expandable up to 17K if an external SRAM is used. These MAC addresses are shared
among all eight ports.
The initialization and configuration of the switch is programmed by an external EEPROM. Field
reconfiguration can be achieved by using a parallel interface to reprogram the EEPROM.
The AL15 supports port based VLAN. The VLAN register set is used to configure the destination
ports for multicast and broadcast frames.
The AL15 operates only in the store and forward mode. The entire frame is checked for error and
any frames with errors are automatically filtered and will not be forwarded to the destination port.
The device also provides two levels of security for intrusion protection which can be implemented
on a per port basis.
The AL15 also features port monitoring and broadcast storm throttling.
PDF 
ZIP