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7.4
RD85 VIDEO SELECTION MODULE
The RD85 video switching module is a single channel video switcher. It can select any
of the 32 video input signals (from the mother board video buss) or it's own cascade
video input (used when stacking multiple video switching subracks). All video switching
is vertical interval and in addition, a clamp-to-black period can be inserted at the
switching transition to HIDE any frame roll that may occur for unsynchronized video
signals. The video output from the RD85 module is fully DC restored for all video source
selections.
7.4.1
Operation
The RD85 video switching module is designed for use in any of the MAXPRO-Net video
switching subracks. One RD85 module is used for every channel of video switching
required (per subrack) or 32 inputs of full matrix.
The subrack control microprocessor (RD105B) manages the operation of every RD85
module used within the subrack. Video switching commands are sent from the
MAXPRO-Net system control computer to the subrack control microprocessor (RD105B).
The command is then decoded by the RD105B. The actual number of the video input
required is then written to the appropriate RD85 video switching module, causing the
new video source to be selected by that channel.
7.4.2
Vertical Interval Switching
When a new video input selection is written to the RD85 module, it is firstly stored in a
primary-latch. Note, this new video source number has not been selected yet. When the
next vertical interval sync pulse occurs (of the currently selected video signal), the new
video source number is transferred into a secondary-latch that actually makes the new
video source selection. The new video signal is now selected by the RD85 module and
available from its video output connector. This method of vertical interval switching
assumes that all video source signals are all vertically synchronized. If they are not, then
frame roll may still occur. Where no video signal was selected previously, the new video
source selection is made immediately.
Rev. C
7.4-1
HMXMU001018
10/06
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