Crystal Vision
Introduction
DEC105S User Manual R1.1
5
15/12/04
Output timing
Horizontal and vertical timing adjustments are provided which operate relative to one of
three analogue timing references. These are an external reference, the video input or an
internal free-running clock. The external reference can be video or composite syncs
although a composite black and burst plus 300mV syncs into 75Ohm as per EBU N14-
1988 is to be preferred.
If no analogue reference is provided the board will either time itself relative to the
composite or Y/C video input in 10 bit modes, or it will time its output to a free running
clock in 8 bit modes.
A horizontal offset delay adjustment varies the timing of the input video relative to input
syncs and blanking in 10 bit mode whichever source is the active reference.
Audio follow pulse
To allow an audio delay to track the video delay through the DEC105S, a TTL level pulse
is provided. This audio follow pulse is available from GPI5 and from a BNC socket on the
RM27 rear module. This pulse is output every frame. The length of the pulse (the time
between the rising and falling edge) is the same as the delay through the synchroniser.
General Purpose Interface (GPI)
The DEC105S, as with most Crystal Vision modules, is equipped with GPI control I/O.
GPI
Low (<1V)
High (+5V)
0
‘a’ No connect
1
‘b’ 8 bit lock
Loss of 8 bit lock
8 bit locked
2
‘c’ SDI present
No SDI present
SDI present
3
‘d’ Reference present
No reference present
Reference present
4
‘e’ Input standard
625
525
5
‘f’ Audio follow pulse
Pulse width equal to audio delay
As supplied, each GPI output has a 330Ohm resistor in series with its output. This allows
for an external LED to be driven, connected to a dc voltage of +5V.
