Appendix F: Edid Definitions And Ddc Modes - Thinklogical VelocityKVM-5 Product Manual

Appendix F: EDID Definition and DDC Modes
E D
xtended
(manufacturer's name, product type, serial number, etc.) and capabilities (native timing, frequency range, video and audio formats, etc.) to a video source.
EDID is what enables a modern personal computer to know what kind of monitor is connected.
With this information the CPU and video card can determine what resolutions the monitor is capable of. EDID is defined by a standard
published by the Video Electronics Standards Association (VESA). The EDID also includes such information as the phosphor or filter
type, timings supported by the display, display size, luminance data and pixel mapping data for digital displays.
Display Data Channel (DDC)
and can be either unidirectional or bidirectional.
A bidirectional bus supports content protection (HDCP) and display calibration software.
Protection is a specification used to encrypt and protect digital video and audio signals transmitted between two HDCP-enabled devices.)
Default DDC Modes:
Remote Dynamic Mode
The unit acts as a direct connection between the RX and TX. In this mode DDC data is read at the RX and sent to the TX. Once verified at the TX the
information is written into a PROM on the TX and provided to the CPU video card. The RX will not send DDC data to the TX unless a different display
is connected to the RX.
Advantage: Allows CPU video card to boot when there is no fiber connection to the RX.
Limitations: No communication link from the CPU to the display. Remote Dynamic prevents the use of HDCP or monitor configuration /color tuning.
Remote Static Mode
Remote Static Mode is a subset of Dynamic Mode in that once a transfer from the RX to the TX is completed successfully, no other transfer will be
made unless specifically requested. The DDC data stored in the TX PROM will not change regardless of display changes.
Advantage: Allows the user to acquire and use an EDID table regardless of changes in connection at the RX.
Limitations: No communication link from the CPU to the display. Remote Static prevents the use of HDCP or monitor configuration/color tuning. This
may result in no video if a display with lower resolution capability is subsequently connected.
Pass-Thru Mode
The units act as a direct connection between the TX and RX. This mode allows the CPU to communicate directly with the monitor.
Advantage: Allows monitor color tuning and HDCP.
Limitations: If a monitor is not connected to the RX, most video cards will not boot.
Local Static Mode
Local Static mode operates in the same manner as Remote Static mode, except that the EDID table is read from a monitor plugged into the
local port of the TX. The TX will read the DDC from the locally connected monitor until it reads a valid EDID table. The table will then be
stored on the TX and presented to the CPU.
Advantages: The TX does not need to be connected to the video card or RX. The EDID table can be loaded before the TX is installed.
Limitations: No communication link from the CPU to the display. This prevents the use of HDCP or monitor configuration/color tuning and may result
in loss of remote video if a display with lower resolution capability is connected to the RX.
Default EDID Table
Two EDID Tables are present. One supports resolutions of 1920x1200 and the other supports 1920x1080.
Advantage: Sends a valid EDID table to the CPU to boot the graphics adapter .
Limitations: Default EDID table may not support required resolutions.
Feature
Remote Dynamic
Supports HDCP
Supports
Monitor
calibration
Monitor on Rx
side required to
boot video
EDID table
loaded from Rx
EDID table
loaded from Tx
EDID table stored
in non-volatile
memory
V e l o c i t y K V M E x t e n d e r P r o d u c t M a n u a l , R e v .
I D
isplay dentification ata (EDID)
is a VESA standard transport medium between a CPU's graphics adapter and monitor used to pass EDID,
Load Default EDID Table
Remote Static
Pass-Thru
Yes Yes No
No No Yes
No No
Yes
Yes Yes No
No No
No
Yes Yes No
is a data structure provided by a digital display to describe its identity
(High-bandwidth Digital Content
Load Default
Local Static
Yes Yes
No No
No No
No No
Yes No
NOTE: Most DVI-D
graphics adapters will
not boot if a valid EDID
Yes Yes
table is not received at
power up.
C , F e b r u a r y , 2 0 1 7
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