Functional Description
10.5.2.1.2 TMDS Capabilities
The GMCH is compliant with DVI Specification 1.0. When combined with a DVI
compliant external device and connector, the GMCH has a high speed interface to a
digital display (e.g., flat panel or digital CRT). When combining the two multiplexed
SDVO ports, the GMCH can drive a flat panel up to 2048x1536 or a dCRT/HDTV up to
1920x1080. Flat Panel is a fixed resolution display. The GMCH supports panel fitting in
the transmitter, receiver or an external device, but has no native panel fitting
capabilities. The GMCH will however, provide unscaled mode where the display is
centered on the panel.
10.5.2.1.3 LVDS Capabilities
The GMCH may use the multiplexed SDVO ports to drive an LVDS transmitter. Flat
Panel is a fixed resolution display. The GMCH supports panel fitting in the transmitter,
receiver or an external device, as well as using a built in 3x3 panel scalar for a single
SDVO port.
10.5.2.1.4 TV-Out Capabilities
Although traditional TVs are not digital displays, the GMCH uses a digital display
channel to communicate with a TV-Out transmitter. For that reason, the GMCH
considers a TV-Output to be a digital display. The GMCH supports NTSC/PAL/SECAM
standard definition formats. The GMCH generates the proper timing for the external
encoder. The external encoder is responsible for generation of the proper format
signal. Since the multiplexed SDVO interface is a NTSC/PAL/SECAM display on the TV-
out port can be configured to be the boot device. It is necessary to ensure that
appropriate BIOS support is provided. If EasyLink is supported in the GMCH, then this
mechanism could be used to interrogate the display device.
The TV-out interface on GMCH is addressable as a master device. This allows an
external TV encoder device to drive a pixel clock signal on SDVO_TVClk[+/-] that the
GMCH uses as a reference frequency. The frequency of this clock is dependent on the
output resolution required.
Flicker Filter and Overscan Compensation
The overscan compensation scaling and the flicker filter is done in the external TV
encoder chip. Care must be taken to allow for support of TV sets with high
performance de-interlacers and progressive scan displays connected to by way of a
non-interlaced signal. Timing will be generated with pixel granularity to allow more
overscan ratios to be supported.
Direct YUV from Overlay
When source material is in the YUV format and is destined for a device that can take
YUV format data in, it is desired to send the data without converting it to RGB. This
avoids the truncation errors associated with multiple color conversion steps. The
common situation will be that the overlay source data is in the YUV format and will
bypass the conversion to RBG as it is sent to the TV port directly.
Datasheet
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