Avocent Emerge EMS2000 series, Инструкция по установке и эксплуатации

Страница: 13 / 48

Chapter 1: Product Overview
5
Support for DDC (Display Data Channel)
The Display Data Channel standard allows video monitors to define their characteristics so that
the source computers to which they are connected can optimize their video outputs accordingly.
By their nature, the Emerge EMS2000 extenders enable multiple video displays to be attached to
a single source computer. This causes a complication for handling the DDC standard, however, in
characteristic style we have devised an elegant solution, as detailed below.
Whenever an Emerge EMS transmitter is powered on, it checks its local video port for a working
display monitor with DDC information. The following rules are used to determine the outcome:
a series of strictly ordered actions occur to automatically locate the most suitable DDC data:
• If a display monitor is discovered on the local video port of the transmitter, the DDC data are
cloned from it and stored within the transmitter.
• If no display monitor is discovered on the local video port of the transmitter, the DDC data
held within the transmitter will remain unchanged.
• If the DDC data or clock lines of the transmitter’s local video port are discovered to be
connected to ground, then a default set of DDC data will be reloaded and used.
After the initial search period, the stored DDC data are then presented to the video port of the
source computer. When transmitters are cascaded, only the primary transmitter (the one connected
to the source computer) will perform the search for DDC data.
EMS2000 transmitters hold two pages of DDC data in order to support the most advanced display
monitors. The DDC data are held within non-volatile memory so that they are retained when
power is removed.
The manner in which the transmitters search for suitable ‘DDC donors’ could have an impact if
your installation contains display units with differing capabilities. Generally, you should arrange
for the display monitor with the most representative capabilities of your whole installation to
be the one that the transmitter locates on its local port, either initially (and temporarily) while
commissioning or permanently.