The SWITCHFLYW control signal is used in applications
where the data input to the GS9021 is switched between
two synchronous signals. In this case, the two signals may
be slightly misaligned and would normally require the
flywheel to completely re-synchronize. In this scenario, the
re-synchronization time would be undesirable. Asserting the
SWITCHFLYW bit of the HOSTIF write table HIGH allows the
flywheel to re-synchronize to the new incoming signal at the
end of the switching line. For this functionality to operate
properly, the two signals must both be in the active picture
portion of the switching line at the time of the switch.
2.2 Accurate FVH Timing Signals
The lines on which the LOW to HIGH transition occurs
conform to the SMPTE standards.
STANDARD
NTSC 4:2:2 Component
(13.5MHz Y sampling)
NTSC 4:2:2 16x9 Widescreen
(18MHz Y sampling)
NTSC 4:4:4:4 Single Link
(13.5MHz Y sampling)
PAL 4:2:2 Component
(13.5MHz Y sampling)
VBLANKS/L=1
9/272
VBLANKS/L=0
19/282
GS9021
9/272
19/282
9/272
19/282
22/335
22/335
PIN
F[2:0]
V
H
VBLANKS/L
LOGIC OPR
HOST BIT
F[2:0]
PAL 4:2:2 16x9 Widescreen
(18MHz Y sampling)
PAL 4:4:4:4 Single Link
(13.5MHz Y sampling)
22/335
22/335
22/335
22/335
AND
VBLANKS/L
For composite based standards, the V output signal is
asserted HIGH as described in the table below:
The F[2:0] signals indicate the current field of the video
data. Three F bits are necessary to accommodate the
composite PAL standard which has 8 fields. For component
standards only F0 is used to represent F = 0 or F = 1. The
F[2:0] bits are available on dedicated output pins and via
the HOSTIF read table. Figure 4a and 4b illustrate the
position of the F[2:0] transition within a line for component
and composite signals, respectively. The lines on which the
transitions occur conform to the SMPTE standards.
For component signals, the horizontal (H) signal is HIGH
during the horizontal blanking region of the output signal,
from EAV to SAV inclusive. For composite signals, the H
signal remains HIGH only for the 3FF, 000, 000, 000, and
TRSID words. Figure 4a and 4b illustrate the H output signal
timing for component and composite signals, respectively.
The vertical (V) signal timing is dependent on the incoming
video standard and the VBLANKS/L control signal. The
VBLANKS/L signal is available as an input pin and via the
HOSTIF write table and should be set to indicate the form of
the incoming data stream. This allows the flywheel to
correctly structure the V bit for flywheel synchronization,
TRS insertion, and TRS error indication.
For component based standards, the transition of the V
output signal within a line is shown in Figure 4a. The line on
which the V output signal transitions from HIGH to LOW is
summarized in the following table.
VBLANKS/L=1
NTSC
Composite
from Line 525/ Sample
768 to Line 9/ Sample
767 inclusive
AND
from Line 263/ Sample
313 to Line 272/
Sample 767 inclusive
VBLANKS/L=1
PAL
Composite
from Line 623/ Sample
382 to Line 5/ Sample
947 inclusive
AND
from Line 310/ Sample
948 to Line 317/
Sample 947 inclusive
VBLANKS/L=0
from Line 525/ Sample
768 to Line 19/ Sample
767 inclusive
AND
from Line 263/ Sample
313 to Line 282/
Sample 767 inclusive
VBLANKS/L=0
from Line 623/ Sample
382 to Line 15/ Sample
947 inclusive
AND
from Line 310/ Sample
948 to Line 327/
Sample 947 inclusive
2.3 TRS Errors
PIN
LOGIC OPR
HOST BIT
TRS_ERROR
The flywheel is also used to indicate TRS errors. These
errors are detected by comparing the TRS in the incoming
data stream with the expected TRS based on the internal
flywheel.
8
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GENNUM [ GENNUM CORPORATION ]
