VITESSE
SEMICONDUCTOR CORPORATION
Data Sheet
VSC850
Features
• 1.6 Gb/s Operation
• Non-blocking Architecture
• Duty-cycle Distortion:
≤
100 pS
•
≤
1.8 nS Propagation Delay for Data Path
•
≤
200 pS Output to Output Skew in Broadcast Mode
1.6 Gb/s 16X32
Crosspoint Switch
• Power Supply: -2 V and 3.3 V
• ECL Differential Data Paths
• 3.3 V TTL Control Signals
• Low Power Dissipation
• Package: 208-pin PQFP
General Description
This VSC850 is a 16 x 32 crosspoint switch intended for high speed digital data communications applica-
tions. This product has 16 data inputs and 32 data outputs. Any input can be multiplexed to any, some, or all out-
puts. High speed digital data up to 1.25 Gb/s can be switched with less than 100 pS pulse width distortion. In
broadcast mode, any two outputs will exhibit less than 200 pS of skew relative to one another. Signals in data
paths are fully differential to minimize duty cycle distortion. The VSC850 requires both -2V and 3.3V power
supplies.
The address signals that control traffic patterns for data paths are double buffered.
LSTROBE
signals load
individual addresses for each output. A GSTROBE signal is used to update addresses for all 32 outputs simulta-
neously. This method allows users to configure any, some or all switches independently without disrupting data
flow of the data paths. A
CONFMODE
signal is provided to allow configuring the array either as a single 16 x
32 matrix or as two parallel 16 x 16 matrix’s. Broadcast and flow through functionality are controlled via
BROADCAST
and
FLOWTHRU
inputs.
This product is ideal for high speed digital applications including data distribution for telecommunications,
fiber channel networking, computer networking, multiprocessor switching, and test equipment. In a telecommu-
nications SONET application, for example, the VSC850 can be used as an STS-12 protection switch.
The VSC850 is packaged in a 208 pin thermally enhanced PQFP 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 VSC850 may be used to connect any one of 16 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-[0:15]
to output channels
Z+/Z-[0:31]
through
thirty-two 16:1 multiplexers. The traffic pattern is controlled by data previously stored in thirty-two 4-bit con-
trol latches each corresponding to an output channel. Value of these 4-bit control latches is a binary numerical
representation of the input channel selected (i.e., 0000 corresponds to
I[0],
0001 corresponds to
I[1],
etc.).
Traffic information stored in control latches can be configured in either Single or Double Configuration
mode by controlling
CONFMODE
input (see Table 1). If
CONFMODE
is high, the switch is configured in Sin-
gle Configuration mode. In this mode, output addresses
A[4:0]
select one out of 32 banks of 4-bit holding regis-
ters. At rising edge of
LSTROBE[0],
this bank of registers is updated by input addresses
D[3:0]
which describes
a new path for that channel. The coding for these addresses is a binary numerical representation.
D[3:0]
= 0000
corresponds to
I[0],
0001 corresponds to
I[1],
etc. Similarly,
A[4:0]
= 00000 selects path to output
Z[0],
00001
to
Z[1],
etc. In this mode, values at
LSTROBE[1], A[7:5]
and
D[7:4]
inputs are ignored. In Double Configura-
G52152-0 Rev. 4.0
6/4/99
©
VITESSE
SEMICONDUCTOR CORPORATION
741 Calle Plano, Camarillo, CA 93012 • 805/388-3700 • FAX: 805/987-5896
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