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HDMI output stage
Please note: Due to the plug and play nature of the
HDMI/DVI interface, if presented with a reported no
HDMI problem it is worth checking all set-up
parameters of both the DVD player and the
Plasma/Projector in use before performing component
level diagnostics on this section.
HDMI is a system that transmits uncompressed digital
video and digital audio over a high speed encrypted
interface.
IC1102
is an
SII9030 HDMI transmitter
IC in essence
the chip takes the Digital Video and Audio information
and sends the Data out in HDMI format.
REG1100
is used to generate a clean regulated 3V3
power supply to Pins 18 and 33 of the HDMI chip.
IC1100 –IC1101 are 3 state octal/line drivers these
form a multiplex that switches between the 2 groups of
signals for the video data input stage of the SII9190
the multiplexer is control by the Signal from the Vaddis
V labelled as PROG/INT this will sit at logic 1 for
Progressive scan and logic 0 for interlaced.
In
interlaced mode
the 8 bit Y/Cb/Cr video data on
VIDP7-0
are passed to input port pins
D15 – D8
of the
SII9190.
In
Progressive scan mode
all 20 bits of the Video
data bus are used and get mapped as follow.
VIDP 19 -12 provide 8 msbits of Y data to pins D15-8
VIDP 11 -10 provide 2Isbits of Y data to pins D2-3
VIDP 9 - 2 provide 8 msbits of Cb/Cr data to pins D23 – 16
VIDP 1 – 0 provide 2 Isbits of Cb/Cr data to pins D7 - 6
Along with the VIDP video data lines we must also see
VSYNC – Vertical sync data
HSYNC – Horizontal sync
CLK27M_VID – 27Mhz video clock.
SPDIF – Digital audio data (Full surround)
MCLK_HDMI – Used to strobe HDMI dig audio
At the
output
of the HDMI chip we will see the
following signals at SKT100.
TMDS (Transistion Minimised Differential Signalling) this
consists of a clock signal (TXC+/TXC-) and 3 data
signals
(TX0+/TX0-, TX1+/TX1- and TX2+/TX2-).
All signals are differential and use current switching
techniques therefore no signals will be observed unless
the output is correctly terminated. In this application the
clock signal will always be 27MHz and the data signals
will be clock X10 so 270Mbit/s.
DDC Channel
this is a 12C interface on DDC_SCL and
DDC_SDA. These signals connect to the VADDIS V
which is the I2C bus master, The DDC channel is used
to read back information from the HDMI sync regarding
it’s Video and Audio capabilities and is also used for
HDCP encryption authentication.
+5V Power, the HDMI interface requires a 5V supply
capable of delivering around 50mA, the supply is
provided by REG 1101 which delivers the required
current and will shut down in the event of a short circuit.
Hotplug.
The HDMI `Hot plug’ signal HDPIN is a +5V to
signal the presence of equipment being connected, this
converted to 3v3 logic 1 as IC1100 is not +5V tolerant.
CEC.
The CEC (Consumer Electronics Control) signal is
a 1-wire bidirectional control signal. It connects to the
Vaddis via an ESD protection circuit D1102 at the
moment this line is not used at present and is an
optional part of the HDMI specification.