The sync board facilitates a variety of operations. The follow-
ing are some tasks that can be accomplished using the
Vertical Interval Sync Expansion board:
Extracting a Master Sync Signal
A system master sync signal can be extracted from any video
input signal which contains vertical sync information. A
video signal provided to the external sync input (P2 on the
board; figures 4.1 and 4.2) is decoded and a TTL vertical sync
pulse containing vertical sync information is provided on the
composite sync output (P4 on the board; figures 4.1 and 4.2).
Any video input signal can be selected as a sync source if one
of the video outputs is connected to the external sync input
(P2 on the board; figures 4.1 and 4.2).
Synchronizing a Multi-Enclosure Switch
The sync board can be used to orchestrate many I/O boards
performing switches simultaneously. Once the sync board is
enabled, the next switching pulse detected is routed to the I/O
boards for switch execution. The sequence of events for the
distribution matrix follows:
First, the master enclosure issues a pending switch command
to all boards for execution upon receipt of the sync pulse.
Second, the master enclosure enables the sync board.
Finally, when the next sync pulse is detected by the sync
board, the switch command is executed by all boards.
4-2
Chapter 4
Figure 4.2 Vertical Interval Sync Expansion Board
(3 rack unit and 4 rack unit enclosures only)
P1 - Input
P2 - Input
P3 - Output
