SIERRA VIDEO SYSTEMS
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Crosspoint Control De-Scrambling
The interconnection between input buffer to crosspoint modules and crosspoint modules to output
drives is determined for optimal signal performance. This interconnection results in a "scrambled"
sequence of connections to the inputs and outputs of each crosspoint and output module. This is
handled by using de-scrambling look-up table that is part of the control interface in the Sequoia
processors. The de-scrambling results in the control processor addressing the switching
hardware in correct manor. This is a very important concept to understand in the maintenance
and trouble-shooting of the internal control system.
A configuration file is loaded into the Sequoia processor by the factory before shipment, and is
also provided on an accompanying CD. If the processors lose this information, it can be reloaded
using GRIP software or generic terminal software running on an IBM compatible PC.
The de-scrambling process is different for each and every Sequoia router configuration. As part of
the circuit description and schematic diagrams for the crosspoint modules, Sierra Video Systems
include the de-scrambling lists for each module.
Analog Video Signal Path Overview
The Sequoia Series analog video routers are based on a conventional “two stage” crosspoint
matrix design. The signal path consists of three elements or modules:
32 Input module
128 x 64 crosspoint module
4X1X32 Output module
Each input buffer assembly consists of a PCB which is installed and removed from the front of the
router frame. Rear panel BNC connectors pass through intermediate connectors to 32 buffers
which individually isolate incoming video signals, providing correct terminations to external
sources and providing 50 Ohm source impedance signals for crosspoint assemblies. One or two
50 Ohm impedance coaxial ribbon cables connect the 32 outputs of each input buffer assembly to
one or two 128X64 crosspoint assemblies.
128X64 crosspoint assemblies accept up to (4) 32 signal ribbon cables from input boards, or up
to 128 signals from a crosspoint backplane bus, which can be driven by a crosspoint board to
which input cables have been attached. One or two 32 signal coaxial ribbon cables leave each
crosspoint assembly and connect to output assemblies.
4X1X32 output assemblies consist of (32) 4X1 switchers and output buffers which pass through
intermediate connectors to reach rear panel BNC connectors. 1 to (4) 32 signal coaxial ribbon
cables arrive at each output board from up to (4) 128X64 crosspoint assemblies. This allows each
output to connect to 4X128 or 512 inputs in the three board system.
For a 128 x 128 system, there will be 4 input cards, 2 crosspoint cards, and 4 output cards. For a
256 x 256 frame there will be 8 input cards, 8 crosspoint cards, and 8 output cards. In a 512X512
router, there will be 16 input cards, 32 crosspoint cards, and 16 output cards.
