Intel 6 SERIES CHIPSET - DATASHEET 01-2011 Datasheet page 255

Functional Description
5.26.1.1 Integrated RAMDAC
The display function contains a RAM-based Digital-to-Analog Converter (RAMDAC) that
transforms the digital data from the graphics and video subsystems to analog data for
the VGA monitor. The PCH's integrated 340.4 MHz RAMDAC supports resolutions up to
2048x1536 at 75 Hz. Three 8-bit DACs provide the R, G, and B signals to the monitor.
5.26.1.1.1 Sync Signals
HSYNC and VSYNC signals are digital and conform to TTL signal levels at the connector.
Since these levels cannot be generated internal to the device, external level shifting
buffers are required. These signals can be polarity adjusted and individually disabled in
one of the two possible states. The sync signals should power up disabled in the high
state. No composite sync or special flat panel sync support are included.
5.26.1.1.2 VESA/VGA Mode
VESA/VGA mode provides compatibility for pre-existing software that set the display
mode using the VGA CRTC registers. Timings are generated based on the VGA register
values and the timing generator registers are not used.
5.26.1.2 DDC (Display Data Channel)
DDC is a standard defined by VESA. Its purpose is to allow communication between the
host system and display. Both configuration and control information can be exchanged
allowing plug- and-play systems to be realized. Support for DDC 1 and 2 is imple-
mented. The PCH uses the DDC_CLK and DDC_DATA signals to communicate with the
analog monitor. The PCH will generate these signals at 2.5 V. External pull-up resistors
and level shifting circuitry should be implemented on the board.
5.26.2 Digital Display Interfaces
The PCH can drive a number of digital interfaces natively. The Digital Ports B, C, and/or
D can be configured to drive HDMI, DVI, DisplayPort, and Embedded DisplayPort (port
D only). The PCH provides a dedicated port for Digital Port LVDS (mobile only).
5.26.2.1 LVDS (Mobile only)
LVDS for flat panel is compatible with the ANSI/TIA/EIA-644 specification. This is an
electrical standard only defining driver output characteristics and receiver input
characteristics.
Each channel supports transmit clock frequency ranges from 25 MHz to 112 MHz, which
provides a throughput of up to 784 Mbps on each data output and up to 112 MP/s on
the input. When using both channels, each carry a portion of the data; thus, doubling
the throughput to a maximum theoretical pixel rate of 224 MP/s.
There are two LVDS transmitter channels (Channel A and Channel B) in the LVDS
interface. Channel A and Channel B consist of 4-data pairs and a clock pair each.
The LVDS data pair is used to transfer pixel data as well as the LCD timing control
signals.
Figure 5-13
Datasheet
shows a pair of LVDS signals and swing voltage.
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