7
Technical manual
7.1
DVI routing
DXS-XX is build to route DVI video signals (and their implicit display info) from inputs to outputs. It approves
DVI1.0 standard, having the maximum transfer rate of 1.65GBit/s on every video data differential line. With that,
you can have video resolutions of up to 1920x1200 Pixels (at 60Hz repetition rate) on each of the inputs and
outputs.
Transporting that high data rates over copper cables will lead to signal (and content) degradation, the more the
longer the cables become and the higher the resolutions are. To compensate that “cable loss”, DXS-XX has adap-
tive cable equalizers on every input port. As the equalisation is adjusted permanentely and automatically, no user
interaction is required. Using this equalizers will extend the cable length at each input to more than 35m at
maximum DVI resolution, high quality cables assumed.
After the signal improvement the video signal of each input is routed to a dedicated, special crosspoint routing
chip. This chip is able to route the video signal to one or many of its outputs. When routing only to one output,
this will set up a point-to-point interconnection, if it routes one signal to many outputs, this makes a point-to-
multipoint connection (diversity function).
The routing chip is a non-blocking switch, i.e. existing routings do not block / prevent new routings of other in-
puts or outputs. Only one major rule will apply: one output can only show maximum one input. If you select a
new input for an output, the existing routing will break before making the new connection.
If you add a new output to a already routed input (i.e. already leads to another output port, too), the existing
routing will not show any interrupt or signal errors.
All output signals leaving the routing chip are buffered with line drivers before going the the port’s DVI connec-
tor. This will allow maximum cable length with good signal integrity at each output.
7.2
EDID handling
The DVI standard defines, that every DVI video source has to be able to find out the video features of a DVI
compliant displaying device. The idea behind is, that the source will find out, what resolutions (in size and timing)
are supported by the display, and then only send out “supported” timings and signals, so that the display will
always show best possible content.
To find out the display’s information dataset, there has to be a so called “DDC” (display data channel), which is
implemented between source and sink of a DVI video system. Technically speaking, there is a I²C-Interface be-
tween source and sink, and a protocoll specification, how the source can read and interpret display’s information
data. Many publications call this dataset “EDID”, an acronym for “extended display information data”. This man-
ual will follow this definition.
As mentioned above, every displaying device has to provide EDID information when it is compliant to DVI stan-
dard. As DXS-XX acts as display device, seen from any video sources (like PCs), DXS-XX must provide EDID info
compliant to DVI standards at any time. Even if DXS-XX is de-energized, it has to provide that info! To fullfill
these requirements, a sophisticated EDID handling is built into DXS-XX.
EDID handling is required for every input separately, so setup of EDID behaviour is available for each of the in-
puts present separately. You can set up these modes of operation:
A)
EDID emulation („STATIC“):
The DVI input has a valid, static EDID information, that never changes automatically. The EDID con-
tent can be a factory default or any EDID information that is read back from an attached displaying
device (which MUST provide an EDID). The static information on each DVI input port is available for
a video source even if DXS-XX is de-energized; the video source provides a small supply voltage
through the DVI cable.
B)
EDID follow („FOLLOW“):
Having that mode, the DVI input holds a copy of the currently assigned output display’s EDID info. If
the input is routed to two or more outputs (point-to-multipoint configuration) , the output with the
lowest channel number will be the one used as source of EDID. If a change in routing occurs (with
Содержание DXS-44
Страница 7: ......
