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 product.
HDMI is a system that transmits uncompressed digital
video and digital audio over a high speed encrypted
interface.
IC1102
is an
SII9190 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
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
unledd 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 a optional
part of the HDMI specification.
Comms and Final video output stage
The signals from the main board travel up to the Comms
board on connector
CON902
.
The
Video signals
simply travel via an A-C coupling net
before exiting the player via the RCA-phono sockets at
locations
SKT902
and
SKT903
.
The
RS232
interface is on 9 way “D” type CON900, with
IC900 providing the level translation and static protection
between the RS232 levels and the
3.3V
CMOS levels
required by the VADDIS V,
CON900
also supplies a
+5V
Status level when ever the unit is not in standby this
generated from a buffered version of the
AV_ENABLE
signal as used within the SCART output stage (0V in
standby).
We have two remote input bus’s on this board, the first
can be seen to arrive at
SK901
on a 3.5mm mono jack
signal received should be a
36Khz
modulated RC5
signal, the RC5 data then travels to the front panel and
is fed to IR led that is sited just behind the front panel
IR
Sensor
, we use the sensor to demodulate the and opto-
isolate the signal due to the fact that the signal is floating
up from ground.
The 3.5mm socket at location
SKT900
is used to receive
un-modulated RC5 signals these take the form of a
5V/0V RC5 signal, with 5V representing a mark
(equivalent to a burst of 36Khz carrier on infrared) and
the 0V representing a space (equivalent to no-infra-red
carrier), this input is effectively wire-Ord with the front
panel IR receiver on
IRRCV
.
