JANUARY 2010
13
REVISION C
Once informed of a DDC change the TX reads the DDC information from the RX. If the DDC from the
RX is different from that stored in the TX non-volatile memory, the TX writes the new DDC information to
non-volatile memory that the video card can read. The TX then informs the video card that the DDC
information has changed so that the video card can read the DDC and act accordingly. In this mode the
CPU may be booted up with the TX turned off or disconnected from the RX since the TX non-volatile
DDC memory can be read by the video card without TX power.
3.5.1.2 Static Mode
Static DDC mode is typically used in switching situations.
In some switching situations the customer
may be using multiple monitors that are all capable of handling the same video resolution but some of
the monitors in the system may cause the video card to turn off the video output. Another possible use of
Static DDC mode is when a video card does not recover from a video cable being hot-plugged while the
system is booted. Static mode resolves these issues by preventing the TX from writing to the non-
volatile DDC memory stored on the TX and static mode prevents the TX from informing the video card of
a change in DDC data. In this mode the CPU may be booted up with the TX off or disconnected from
the RX since the TX non-volatile DDC memory can be read by the video card without TX power.
3.5.1.3 Pass Thru DDC Mode
Pass Thru DDC mode gives the video card direct access to the monitor connected to the RX
.
This
mode is useful in HDCP (
H
igh-bandwidth
D
igital
C
ontent
P
rotection) applications. In Pass Thru DDC
mode the video card can directly
write-to
and
read-from
the monitor. The video card will be informed of
the presence or absence of a connected monitor. In this mode there must be a valid data communication
path between the CPU and a connected monitor before the CPU can be booted.
When a Thinklogical
™ product is supplied to customers it typically comes with a default table that
provides a maximum resolution of 1920x1200. If the customer elects to use the default DDC data in
static mode, the video card will read that the TX (emulating a monitor) is capable of showing 1920x1200.
If the monitor connected at the RX cannot display a resolution as high as 1920x1200 the monitor will not
display an image.
