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VSC851

1.6 Gb/s 32 X 32 Crosspoint Switch

Vitesse Semiconductor 

VITESSE

SEMICONDUCTOR CORPORATION

Data Sheet

VSC851

1.6 Gb/s 32 X 32

Crosspoint Switch

Features

• 1.6Gb/s Operation

• Power Supply: -2 V and 3.3 V

• Non-blocking Architecture

• ECL Differential Data Paths

• Duty-cycle Distortion: ≤ 150pS

• 3.3 V TTL Control Signals

• ≤ 2nS Propagation Delay for Data Path

• Low Power Dissipation

• ≤ 250pS Output to Output Skew in Broadcast Mode

• Package: 256-pin LDCC

General Description

This VSC851 is a 32 x 32 crosspoint switch intended for high speed digital data communications applica-

tions. This product has 32 data inputs and 32 data outputs. Any input can be multiplexed to any, some, or all out-

puts. High speed digital data up to 1.6Gb/s can be switched with less than 150pS pulse width distortion. In

broadcast mode, any two outputs will exhibit less than 250pS of skew relative to one another. Signals in data

paths are fully differential to minimize duty cycle distortion. The VSC851 requires both -2V and 3.3V power

supplies.

The address signals that control traffic patterns for data paths are double buffered. the LSTROBE signal load

individual addresses for each output. The GSTROBE signal is used to update addresses for all 32 outputs simul-

taneously. This method allows users to configure any, some or all switches independently without disrupting

data flow of the data paths. Broadcast and flow through functionality are controlled via BROADCAST and

FLOWTHRU inputs.

This product is ideal for high speed digital applications including Gigabit Ethernet and ATM switch cores,

data distribution for telecommunications, fiber channel networking, computer networking, multiprocessor

switching, and test equipment. In a telecommunications SONET application, for example, the VSC851 can be

used as an STS-12 protection switch.

The VSC851 is packaged in a 256 pin thermally enhanced LDCC package. This product is fabricated using

Vitesse’s E/D GaAs MESFET process which achieves high speed coupled with low power dissipation.

Functional Description

The VSC851 may be used to connect any one of 32 inputs to any one or combination of 32 output channels,

according to a user defined bit pattern stored in each output channel’s control latches (see Figure 1). For data

path operation, signals flow transparently from inputs I+/I-[0:31] to output channels Z+/Z-[0:31] through

thirty-two 32:1 multiplexers. The traffic pattern is controlled by data previously stored in thirty-two 5-bit con-

trol latches each corresponding to an output channel. Value of these 5-bit control latches is a binary numerical

representation of the input channel selected. D[4:0] = 00000 corresponds to I[0], D[4:0] = 00001 corresponds

to I[1], etc. Similarly, A [4:0] = 00000 selects path to output Z [0], A [4:0] = 00001 to Z [1], etc. To configure

the switch, at rising edge of LSTROBE, the bank of holding registers for a particular channel is updated by input

addresses D[4:0] which describes a new path for that channel. After some or all holding registers are pro-

grammed, a high pulse is applied to GSTROBE to transfer the information from holding registers into all control

latches. By this method, the entire crosspoint switch can be reconfigured simultaneously.

G52167-0 Rev. 4.1

10/21/99

© VITESSE SEMICONDUCTOR CORPORATION

741 Calle Plano, Camarillo, CA 93012 • 805/388-3700 • FAX: 805/987-5896

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