dss-084
TVDET
TVINT
TV disconnected
TV connected
TV disconnected
cvideo1_out
(vertical sync pulse)
Start of
sync pulse
Start of
sync pulse
End of
sync pulse
End of
sync pulse
Load
detection
Status of the load is latched
to the output on the 2nd rising
edge of TVDET
Load
detection
Tdm
Tdm
Status of the load is latched
to the output on the 1st rising
edge of TVDET
Public Version
www.ti.com
Display Subsystem Functional Description
Figure 7-111. AC-Coupling TV Detect Waveforms for TV Connected and Disconnected
NOTE:
•
When setting the DSS.
register, software
users must ensure that the TVDET signal is in the active area. To avoid any problem,
the TVDET signal must not be longer than one line.
•
The activation of the TVDET signal will not have a visual impact on the cvideo1_out
output signal.
7.4.7.9.5 TV Detection/Disconnection Usage
The TV-detection/TV-disconnection is based on the difference in voltage levels in the output of the TV
buffer depending on the load status. The operation is slightly different for ac and for dc operation. For DC
operation, the cvideo1_out voltage is compared against a voltage reference that makes the comparator
trigger in each sync pulse while the load is connected. For AC operation, the cvideo1_out voltage is
compared against a voltage reference that makes the comparator trigger in each sync pulse while the load
is disconnected. In both cases, the TVINT output signal produces a logic 1 when a load is connected and
a logic 0 when a load is disconnected.
For DC-coupling mode, see
and for AC-coupling mode, see
NOTE:
Because the video DAC stage and the video encoder must be awake for connection
detection, consider that the video DAC stage can take up to 10 µs to wake up.
1701
SWPU177N – December 2009 – Revised November 2010
Display Subsystem
Copyright © 2009–2010, Texas Instruments Incorporated
Содержание OMAP36 Series
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