Tektronix Digital Video Switcher User Manual

3-29

The basic functions of the Sync Generator Module are: 

■

Use the input reference video to lock the switcher 

■

Generate sync pulses for the other modules in the system 

■

Generate clocks for the other modules in the system 

■

Generate “Sync Edge” pulse for analog input alignment

The input is the analog reference video signal. This signal is brought in as 
a differential video signal from the Communications I/O Module at the 
rear of the frame. The video is filtered, then sync is stripped off. The sync 
is used to lock a 13.5 MHz phase-locked loop. The 13.5 MHz signal is used 
to lock a four times 13.5 clock from which all sync pulses are derived.

The two clocks generated on this module are “system clock” and 
“multiplex clock” which is twice the frequency of “system clock.” These 
clocks have a separate driver for each module. The clock outputs are 
differential positive ECL level. The multiplex clock is used on the modules 
to multiplex and demultiplex the video signals. The system clock is used to 
clock the video through the system. 

The system sync pulses are a TTL level and are generated from the four 
times 13.5MHz phase lock loop. There are two separate generators, one for 
the vertical rate signals and one for the horizontal rate signals. The sync 
pulses have drivers that feed four or five modules. 

The “dither” mode line is controlled on the Sync Generator Module 
through the VID interface. 

Switches:

■

Clock Frequency 13.5 MHz 

■

Field Rate 50 Hz or 60 Hz select 

■

Tally Control Module reset 

■

Horizontal timing (three switches)