General Description
The XpressFlow Engine contains the switching data base interface and buffer management logic in order to do the switching decision making for unicast, multicast, and broadcast frames. Hardware assisted queue manager is incorporated to facilitate buffer management. It also provides a generic Management Bus interface to allow external processor to do initialization, learning, VLAN, and RMON support, etc. In addition, a XpressFlow Bus interface block is responsible for communicating with the Network Access Controllers through the XpressFlow message passing protocol.

Distinctive Characteristics
◆ Highly integrated central switch controller
◆ State of the art 0.35 micron 3.3 Volt CMOS process
◆ 256-PIN PQFP package
◆ Operating frequency
    ◇ -40 40 MHz maximum
    ◇ -50 50 MHz maximum
    ◇ -66 66 MHz maximum
◆ 16-bit external CAM interface
    ◇ Supports ½k to 16k MAC addresses
◆ 32-bit Control Buffer Memory interface
    ◇ Supports 128k to 1M bytes
    ◇ Utilize high performance 32-bit Synchronous Burst SRAM
◆ Hardware assisted Buffer and Queue Management to minimize CPU overhead
◆ 32-bit Management Bus I/O interface
    ◇ Allows host to access CAM and Control Buffer Memory
    ◇ Supports Big and Little Endian CPUs
    ◇ Direct interface with various different standard microprocessors including 386, 486 families and Motorola MPC series embedded processors
◆ 32-bit XpressFlow Bus Interface
    ◇ Switching bandwidth
        -1.28 Gbps @ 40 MHz system clock
        -1.60 Gbps @ 50 MHz system clock
        -2.10 Gbps @ 66.67 MHz system clock
    ◇ Supports up to 8 Multi-port Network Access Controllers
    ◇ XpressFlow Bus access arbitration
    ◇ XpressFlow Bus data transfer load regulation
◆ Full IP Switching
    ◇ Addresses resolved by SC220
◆ MAC Address Mapping Table
    ◇ Supports either CAM based or SRAM based Switching data base
◆ Built-in address to port resolution
    ◇ Embedded 32-bit HISC™ (High density Instruction Set Core) Processor
    ◇ Optimized architecture for switch applications
    ◇ Loadable firmware for easy upgrade
◆ Supports unicast, multicast, and broadcast frames
◆ Address Filtering
    ◇ Destination & Source MAC address matching & filtering
◆ VLAN classification & verification
    ◇ Up to 62 groups
    ◇ Level 1 and 2 mapping
    ◇ VLAN ID tagging & stripping
    ◇ Auto padding if necessary after stripping
◆ Supports Store-&-Forward Frame Forwarding Mode
◆ Collects statistics for RMON